> that's the current threshold

The current threshold is dumb. The whole premise is dumb. Ebikes don't need legislating beyond enforcing existing laws about cycling on sidewalks and the like.

>I've gone >50mph on a bicycle, 40mph on level ground. Yes it's possible, but it requires significant effort and you can't accelerate as quickly as an e-bike.

It's also pretty clear that the geometry of the vehicle was not really optimized for such speeds. I don't think anyone going 30+ (commuting, the spandex crowd who rides for fun is a different story) thinks it's ok to be doing that around pedestrians or anything else sketchy. Most of the problems seem to simply be correlation to accessibility of speed to problem demographics, teenagers and the like. You'll have that problem regardless of form factor. 70yr ago the boomers were drunk crashing muscle cars because those were accessible.

>If lots of people (who I assume are very fit) were riding bicycles dangerously, maybe the legislature would make some laws about that. But until it becomes a problem, there's really no need.

Depends wholly on other unrelated demographic factors IMO. What can these people do for the government vs what problems do you cause it is the primary driver of whether you get stomped or pandered to.