You missed the 120 Volt generator part.That would only work if he has a power outage on only one side of the split phase, that rarely happens.
He has a complete power outage, fires up his huge old odd ball 120V generator, he has a manual transfer switch and a CS 120/240V 50 Amp generator inlet.
His generator cord bridges both hots.
His house has no MWBC other than the dishwasher / disposal.
He keeps all his 240V breakers off, HVAC, dryer, range etc.
Yes."Wires it to a single 120V breaker." meaning he connects the other pole to the neutral, I assume?