I don’t think they are similar to e-bikes at all. More unstable with their little wheels, harder to see due to their size and lack of rear lights, much harder to predict (they seem to wander about).Indeed, I think that's what the trials are for. Personally I see them (in speed-restricted form) as posing basically the same risk as e-bikes, and thus that the two should be covered by the same legislation, whether that be by tightening the law on e-bikes or loosening it on scooters. I can see no case for mandatory insurance or helmets etc for one and not the other.
certainly shouldn’t be allowed on the pavement, and dangerous on the road.