First characteristic of a losing argument: claiming all of the experts are
wrong,

Your experts disagree with my experts.
Surely you noticed that?

No - you seemed to imply that not running a charging system was unnatural for
a
boater. You called a "working environment" one that has a charger running.

Normally a battery works in an environment where there is a charger, or an
alternator. Neither the charger nor the alternator runs all the time, but one
or the other will be running when the battery is being charged, which has a
direct bearing on a question regarding the voltage reading of a battery that
has reached a full charge state.

From your perspective, on a sailboat, that may not be true. If you don't have
an auxiliary and you're charging the battery at home in your garage, you're
probably never going to see anything above 12.6 on the boat.