Indeed, there is special equipment required (the jargon/name escapes me at this moment — it’s been years) to connect a generator to the grid and that also automatically disconnects it if it gets too far from the grid frequency.

IIRC the USA grid SLAs are/were not a simple 60 Hz but 60 times n peaks over some period (10 seconds?) dating back to the era of synchronous electric clocks bc changing load could provide some wobble. I am sure it’s possible to provide tighter conformance these days but I wonder if it matters.