Probably about as safe as a flight aboard a 777. No MH or ATS manufacturer warns about, or protects against, the Shore Tie cable going "hot" when the genny is running. I suppose some kind of catastrophic failure could let that happen, but like I said, no warnings or provision against it.
Just NEVER NEVER "back feed" the house by making up a double-male cord and connecting a coach outlet to a house outlet. OK to use the RV to keep your home fridge cold, simply run an extension cord inside and plug direct to it.