Using bow thruster to steer while underway

Mmm... I'd say barely rather than definitely - if she's catching them at all.
Just focus on the brief part of the video at 1:08, when the camera looks on stbd side.
But of course, waves alone are nowhere near enough to estimate the current.

In fact, since you are familiar with that area, I was wondering something that you probably can answer:
Looking at the map, the boat is heading W while going through the cut.
Now, do you have an idea of how fast a westbound current can move in that cut, at worst?

CJ, I lost count of how many times you ask how many boats someone else ran.
Let me try to address that once and for all: you ran more boat of any kind than myself, all other forumites, and just about any other boaters on the planet.
Happy with that?

Frankly speaking, your approach seems to me akin to someone pretending to be a sommelier after drinking three bottles of wine per day throughout his whole life.
But it doesn't work like that: understanding of quality is what really matters, quantity is only good for triggering cirrhosis!

Ok, in this case my previous theory (that also Capt Ralph envisaged) of unresponsive rudder due to a too low STW doesn't hold water, so to speak.
Oh, well. I wasn't thinking to place an order for a N63 anyhow!

Well, In the same arm chair piloting, I wondered if the stabilizer fins were flailing, catching a following wave.
Something was causing that tub to roll and yawl.
Did he place the motor bike up stairs?
SOMETHING was making an easy ride NOT so easy.
I don't think I could induce such an ugly ride if I tried on our ole tub.

I think the speed fluctuation indicates the vessel is going with the current yet slower than the wave period. The waves are building and shortening in period as he enters the "shallows", and his single screw is being overwhelmed by the quartering/following waves. As he cannot steer with throttles and has no chance of keeping the bow on the heading, he's trying to compensate with the bow thruster. He does seem to be oversteering and reacting instead of anticipating the swells. The boat certainly doesn't seem to enjoy the sea conditions.

Videos may have just saved me a lot of money. I think I’ll be scratching one of these off the list and stick to a big SF.

Indeed. Aside from agreeing with your summary, I believe another important factor is the one about stretched Nordhavns that JWY already pointed out, and I hope she doesn't mind if I extend it a bit.
In fact, interestingly, it's like in Dana Point they are the first to be well aware of the inherent flaws in the hull stretching exercise: try to find full (i.e., inclusive of the hull bottom) drawings of their stretched models, if you can. And this is from someone who used to proudly publish complete drawings of their boats, in the past... 'Nuff said.

I am attaching below the only example I ever came across of a comparison between the stretched version (N52, above) and the original hull (N47, below).
If someone has a similar drawing of the N63, I'd gladly have a look at it, but I'm pretty sure that the principle still stands.
Now, I don't think it takes a naval architect to understand that the one and only logic behind taking a 47 feet mould, make it longer, move just the rudder a bit further back, and sell the boat as a 52 footer is that the latter can fetch a higher price.
I mean, it's either one of two things: the 47 design was wrong, or the 52 extension is.

And by the same token, the N43 went through the same maquillage and became the N475, suggesting BTW with such name that it's somewhat bigger than the previous 47, which she isn't - also because the 47 in the meantime became a 52, as just explained. Ain't marketing a beautiful thing?
Back to the 63, as JWY said, she actually comes from a 55 hull, initially stretched to turn her into the 60, and then into the 63.
And the very same trick was used also with bigger models.

Of course, I can't tell how much that is relevant to the boat behavior in the OP video. Who could?
The only way to tell for sure would have been to have the original 55 doing the same route at the same time, and then compare the two videos.
But I think it's safe to tell, as also JWY inferred with her "bit of prejudice" (very kind of you, J!), that these marketing-driven stretched boats can hardly bring any improvement to the original design.
And to my simple mind, it's pretty obvious that anyone who should design a 52' hull from scratch would never place the propeller and the rudder where they are in the drawing below, if it weren't to avoid the investment in a completely new mould.
The same goes for the 475, 60/63, etc., obviously.

I would caution against making any assessment from that video alone. Too many unknowns to make any real determination.

Kind of hard to answer this. The old apples to oranges line. Two way different hull designs is hard to compare also.

I will ad one comment;
Josie and I made a delivery on a Flemming.
Twin 3208 Cats, stabilized and AP.
With good wind and smart 2/3' waves on our stb/aft from Stuart to Jax (Huckins yard), we were rather disappointed in the ride.
As the picture in post #28 above, The Flemming had a rather shallow draft at the transom.
A stern wave would lift the aft. When that 15th and 17th wave would combine under the stern, the stb wheel would vent.
The seas were not really that bad.

Again, happy with our 45 year old Bert. Her big & heavy asp just gets pushed.

Not sure I have experienced what CJ is talking about, but the bottom line for me is that if a hull gets extended it's usually because it is determined after the fact that there needs to be a greater LWL. Improving the ride and/or handling with the extended LWL would be even better if the running gear was re-located appropriately.

I'm sorry my friend, I do have a problem with your line; "it is determined after the fact that there needs to be a greater LWL".
Who determined this, Sales?? Customer request?? Or a proper hull designer??
I do question if a proper hull annalist is involved..
Not just in Pacific Rim MFGs, but any hull lengthen change of any brand.

I'm not expressing total alliance with Skippy Js presentation; I do know, you just don't take a bath tub and make it longer.
There are lots of hydrodynamics that are involved with any in-the-water hull design.
I have experienced this with MLB's. Longer is NOT better.
As per the OP, Still not sure if that is a F'd-up operator or poor bath tub design or both..

I have talked about that Fleming before; maybe not a fraction of what Skippy J has pushed, But since that nite, That boat (after a good clean up) would serve better as an artificial reef donation.
Never again will I push a Fleming offshore in more than an ICW chop.
Name brand, it sucked.

While the waves seem to be pushing the boat around more than I would like for a 63 ft boat, I think the main problem is he is doing a horrible job in anticipating his bow thruster movement. He keeps laying on it until it moves too far and then has to counter steer and reverse the bow thruster to straighten it out. He does this multiple times. As you know, when you bump a boat into gear when docking there is a response time and same with the BT, there is a delay in the boat movement and he just completely messes up the delay timing. And then at least once he seems to forget he is laying on the BT and keeps it on one way and counter steers the other way. It really looks like poor seamanship in not very challenging sea conditions.

I have to say regardless of the helmsmanship, it is not very impressive how that boat handles in quite modest inlet conditions.

I was not endorsing his use of a bow thruster while under way - I assumed that experienced captains such as yourself would know that. I was simply giving my explanation as to why his use of a bow thruster while underway and lack of responding to the delay in boat movement really exacerbated the poor handling of the boat. His use of the BT and counter-steering made the boats handling look worse than it is and the direct result of his poor seamanship. I have never used my bow thruster while underway except docking.

To be honest, watching that video, even with most of the problems attributed to his poor helmsmanship, that appears to be a poor handling 63 ft boat.