Yeah, the challenge is that hybrid design is a moving target. It's in constant evolution. (I always thought of "hybrid" as any combination of electric vehicle with a gasoline engine on board. Pretty broad category in itself. Then add the drive train variations mentioned ... oy vey.)

I am confident that, as a basic assumption, hybrids are by design more efficient as stationary generators. But does that matter much in the unconventional application suggested in the OP? Phew, I can't begin to prove that. Can you even get at all the energy in the main batteries? Some of these run at very high output voltages. That's the first of many question marks.

(Angels dancing is easier, as there are fewer variables. Fat or skinny? Ballroom, break dancing, or mosh pit? Is the pin compliant with ANSI standards?)