I turn off all 12 volt when filling with Propane. When gasing up (Gasoline) I do not. the gas tank filler is a long way from teh fridgt ane at a lower altitude. gasoline vapors are heavier than air so the danger is ... small.. Only danger woudl be if I sprayed the thing. and that's not likely to happen.
With propane the filler is almost directly below the fridge, and though propane is also heavier than air, and there is a shelf (the access door) to add to safety, the pressures involved make the chance of vapor reaching where I do not want it much, much, much, much, higher.
Question on a propane pump jockey test and my not entierly a joke answer.
Q: What happens if you get hte right mix of Propane and Air and there is a spark or fire
A: You land 2 counties over
Class: Laughter
Instructor: Exactly