Thanks for the responses.
Like many others, I have kept the truck 7 pin connected while on shore power but usually the truck is off. It's my understanding that when the key is off, the relay is opened and hence the 12v at the plug is off. Obviously while towing, the relay would be closed so the line energized.
Got an idea that I'm going to test. Maybe tonight (or this weekend), I'm going to hook up shore power to the camper and then using a digital meter, check out the voltage on the 7 pin cable (on the 5er) to see if I get power.
Yes....overthinking gets me in trouble sometimes.