Anything over 350 Watts with a throttle is a moped. JMO I'm pretty sure most people would even go so far as to say anything with a motor is a moped/motorized bicycle...

IMO, To be a bicycle, you must/should have pedal, and the assist should only be a part, a %age of what ever the person puts into, to make the bicycle move, a smaller part that whatever the person riding it puts into the pedalling effort over all...