Originally Posted by MedSailor
It looks though like they're talking about house wiring though which would be 120v or 220v which, I believe, makes a big difference because the lower voltage of the 12v is creating more heat.
Just chiming in on this (which I actually remember talking with you about before):
The voltage of the bus has nothing to do with ampacity or heat. The voltage drop (and heat generated) is the same for 10A at 120V as it is for 10A at 12V over the same wire.
Differences in specification result from the marine environment, and because you just can't tolerate voltage drop when you only have 12 volts to start with. When you have 120V you can drop a couple of them without your load caring.