That makes no sense, yup. Well, maybe Scooters, yes - they usually have their engine mounted in the swingarm instead of the central frame, which reduces vibrations at the handlebar. As for power, that doesnt correlate, eg. I have a 20yrs old KTM single without a dampening balance shaft. It only has 48PS but boy, does it vibrate. 45min ride = tingling feet and hands. So, number of cylinders, crankshaft configuration and number of balance shafts make the difference.

Also: Vibration spectrum and power distribution probably also make a Zuge difference (for the iphone's lens/autofocus mechanism)

Electric motorcycles are also really smooth.