Pilots aren't the only people involved in operating UAVs, nor the only people to benefit from training
Indeed, but I still don't see why ground handling crews, air traffic controllers, forward controllers, troops on the ground etc, need the Watchkeeper to be flying to get their training value.
Their only interaction with the drone in real-life would be via radio communication with the operator /pilot (who could be in a networked simulator for training) or viewing a video feed (which could be synthetic or fed from a surrogate manned platform that wouldn't fall out the sky).