M Q writes:

Ah. So the generator is not actually an AC generator, but probably a DC
generator with an inverter or other electronics to generate the 60Hz AC?

That's right. The generator just has to generate enough power at a
suitable voltage, and the inverter electronics synthesizes 60 Hz sine
waves no matter what speed the engine is running.

I'd guess the "generator" is actually a multiphase alternator whose
output is rectified to DC, for the same reason your car uses an
alternator instead of a DC generator: simple construction, no brushes to
wear.

A normal AC generator would only produce 60Hz if it was running at the
design RPM of 1800 or 3600.
Clever idea.
Probably now economical because of spill over from photovoltaic industry.

And large inverters used on boats, long-haul trucks, etc.

Dave