Looks like this model uses a simple induction motor for the wash pump.
These little PSC motors need a start / run capacitor (item 4200 in exploded view) to operate and have very little starting torque.
I would suggest checking the capacitor before condemning the motor. Also never rule out the impeller being physically stalled by debris like a chicken bone or other food scraps.
The service tech would have just shorted the pump relay to stooge the motor into starting; this method doesn't check the capacitor or any physical blockage of the impeller.
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