While I'm extrapolating from my 2007 to your MH, my generator starts on the house batteries. It would make sense to leave the engine battery alone because getting home is more important than running some electrical stuff. Plus, the engine will charge the house batteries as you drive so that the generator could be started eventually.
Went out last week to take mine for an exercise drive and to run the generator and A/C units since they pull the most current and the engine battery was dead. I used the house battery switch to give me enough juice to start up. It gave me new appreciation for how these crazy, rolling boxes are designed.
2007 391TS UFO Chassis