They get by because there are not enough standards. How many new boat buyers get a survey? And even then I doubt ABYC as recommendations about using start batteries for thrusters
It is amazing that folk will pay for a NEW boat without an independent survey. "It's a new boat, What could be wrong??" I don't think they have any comments on aux battery banks, Just If Used, that all should be tied to a common negative buss and normal electrical recommendations still apply. Good Boy Scout practices that makes sense are usually not recommended. Separate battery banks for options may be more of a class or flag comment but this is beyond my pay grade..
So another fine institution was flushed. Once again; the whims of the few, out weighed the wants of the many. Baden Powell must have rolled in his grave. Long live the memorys, Jacksonville FL BoyScouting and those that served.
Had something similar happened on my boat during the purchase process. House and start banks were paralleled when we sea trialed. Cranking the engines or running the thrusters would kill the electronics. Turned out to be a bad inverter/charger. The charger portion was not working and the inverter would not "pass through" the dock power. So the fans that the boat manager left running at the dock (they were plugged into outlets powered by the inverter) to prevent humidity issues were drawing down both the house bank and the start banks. In my case, I believe someone on the seller's side paralleled all of the battery banks, thinking the issue was with the batteries. Don't parallel your battery banks unless absolutely necessary, as doing so can mask other issues.