Per the Onan 6kW NH Major Service Manual, page 44, fig 57.....
L1 is what you guys are calling "HOT" and L2 is "NEUTRAL/GROUND" - unless someone has monkeyed around inside the generator's bellhousing..

L1 is a single conductor wire sourced from the compounding reactor in the bellhousing and then routed to the breaker on top of the generator.

L2 is two wires coming out of the bellhousing and crimped into a single lug and attached to a single wire going up the flex to the coach.

The L2 to chassis bonding that makes L2 the "GROUND" is shown at the lower left of Fig. 57.

The two "HOTs" on the 50A receptacle inside the coach's shore power cord cubby are bonded together and connected to L1 coming from the genset.

Note that unless you drive a ground rod at your campsite and then bond the coach's electrical ground to it while running the generator then the coach will never be at true electrical ground potential. It'll always be "floating" above true earth ground potential by an unknown amount that varies from instant to instant.

Once again: if some PO has monkeyed with the coach or genset wiring then all bets are off.

--Jim

Jim Miller
1977 Eleganza
1977 Royale
Hamilton, OH