This is a tricky discussion due to the confusion between power, torque and the way different motors handle this. Add a gearbox (Torque Multiplier) and the confusion gets worse. A commercial grinder motor has to do 2 things....start turning and be able to keep turning, plus grind quickly. Motor shafts are "usually" directly connected to the burrs. For an AC motor to start turning and keep turning through pull up torque to max torque, requires a motor of size n....but to grind fast enough might need a motor of size 2n. A motor consuming more watts, so it can do more work.

the same grinder in home use, may require a motor of size n and because it doesn't need to grind in 4 seconds, but 8 seconds a motor of size n is sufficient.

The same grinder with a gearbox able to generate the required torque with a motor of size n/2, might grind in 16s

In all cases the same total work is done over a different unit time The motors can be of size 0.5, 1 or 2. In a grinder of good design, the size of the motor should only dictate it's capacity to do work. If a grinder is prone to stalling, it's because the design of the grinder (or gearing) is such that there is insufficient torque to turn, the power of the motor is not relevant if it does not have the capacity to do any work.

A "give me a lever long enough and I will lift the world" kind of thing...For any specific grinder, the motor power (plus gearbox if any) design, ultimately comes down to, does it have sufficient capacity (torque), to do the work (weight of coffee ground per unit time) required of it.

P.S. It is also important to consider optimum burr "packing" as I call it in the design....which may well affect grind.