As a rider of high performance bikes for many years, there is a world of difference between the 50cc engines in moped in the video and a high performance multi cylinder engine of 800-1200 cc. It also depends on the make and model, an 1800cc Honda 6 cylinder Goldwing is smooth as silk. Engine design, some engine have harmonic balancing counter rotating shafts, firing order makes a big difference. Apple was wise to put out a general warning and let the user determine the amount of vibration.