The fact they listed wattage and actual peak wattage is different doesn't change the fact that an e-bike's power, not whether the throttle is connected to the handle bars or the pedal, is what actually creates fast and dangerous bikes.

If regulation based on power was drafted, it'd be a simple matter of using a voltmeter and galvanometer to see if a bike is compliant with power limits (arguably motors have different efficiencies, but electric motors are close enough to 100% to use this method).