I have no idea how many times I have explained this. The federal definition is NO FASTER than Class 3 because of the way power is limited.Maybe because the old term "speed kills" comes into play. When more and faster bikes hit the roads there will be more accidents and the faster the bike is going the worse the outcome of those accidents will be. Whenever a product leads to deaths and injuries is when the regulations start to happen. There's no need for a bike to go that fast. If you ride to get to work leave a little earlier.
The physics of this are basic. At 20mph the power is limited to that level (ie what would sustain 20mph) which is typically around 300-350W (below the peak power of most speed pedalecs / class 3 models). If you run simulations with typical rider input with that power provided by the motor the typical top commute speed will be from 24 to 28mph. That is not a "speed kills" scenario (pretty much same result as class 3) but those that don't understand this will hyperbole. One definition is better than 3 and I can guarantee insurance will hit class 3 if PFBs is successful at it's regulatory capture game.
The one factor that will continue to provide the most speed for biking is going down a hill. Gravity is a huge power factor but that gets ignored constantly (they literally hit upwards of 70mph during the professional bike races going down hills and most everyday riders are probably hitting 30mph+. It's frustrating when people only look as the assist as a speed factor when it's not even the biggest one.