Understood, but in this (hypothetical) example his mother probably doesn't know exactly what angular velocity or torque are, so making things even simpler with

Understood, but in this (hypothetical) example his mother probably doesn't know exactly what angular velocity or torque are, so making things even simpler with a laymans "power" serves to get the point across. One could include torque in the explanation to which the follow-up is probably "what's torque?". The simpler one goes for that initial understanding, in most cases, the less technically correct one is; by design that helps the newbie learn and build up to a more technically correct understanding later on.