Does a VPWR capacitor on a high-side MOSFET switch guard against inductive kick back?
If there is no diode clamp on the motor to catch back emfs when the motor current is interrupted, that energy in the motor will force current to flow through the parasitic diode of the MOSFET to the VPWR rail. Adding a "soak up" capacitor on the rail ensures that the VPWR rail won't rise very much. However if you have an output clamp this will largely prevent this from happening and a much smaller capacitor can be used on VPWR.