i know this is the US and not anywhere else but from the UK perspective - its not a grey area and I wish people would stop saying it is:
“It is clear what an ebike is, but it’s not clear what it isn’t”
This should be all there is to it, and if you're going to regulate something just fucking do it and enforce it, or don't even bother in the first place otherwise its just a waste of time.
Having worked on, and sold, ebikes (actual, EAPC, cycles) the number one issue we had was people coming in and asking for surrons and similar 'non pedal' type things. If the people in charge of this stuff just took an active approach in enforcement it would be a thousand times easier for Joe Public to manage.