Look at it this way...
A straight blade 30-amp RV connector is not vibration resistant -- the twist-lock resists vibration and accidental pull-out. Japan does NOT have USA types of home receptacles.
The first thing I did with a Yamahahaha diesel 5500 watt water cooled gen 30 years ago was to pull the panel out and replace the 120vac 15-amp receptacles with Marinco 20-amp marine 120-vac blade receptacles.
But touchees void the warranty.
A twist lock to RV adapter long enough to isolate vibration might be the best way to go. Wiring and breaker protection for the generator stator taps is worth the extra money IMHO. Think of voiding the warranty it helps with the financial pain :)