The answer is FALSE.
You cannot assume that the driver of the motorcycle can see you if you are behind or to the side of the motorcycle. Motorcycle forms can be of too low or too high for you and since you are sitting at the back of the driver, the only means he can use to see you is to use a side mirror. If his motorcycle form is lowered, and he only has small side mirrors, it would be impossible for him to see you unless you make adjustments and you forced yourself to change your seat position just to see him.