Well, Here is another set data points....
My 73 23 (S/N 1650) did have a line cord and a plug.
The reefer was not on its own circuit, but that is not what killed it.
The only GFI are those I added.

There is a reason to keep the 120V power available. It just may not be worth the risk. If you have a coach that has the house bank in the front and you are trying to recover it with the buzz box powered from the APU, the line loss though the 25' of #10SAE wire (note - NOT AWG) is enough to make this operation problematic - As in the best charge rate you can get is about 25Amp.

That is my final answer and I don't need to call a friend.

Matt - Just greased his Lenzi hubs for the first time