So at the very least is a real person and appears accurate to his claims
In observing high sensitivity play, it is clear that there is more of an isolation of the hand and wrist in regards to movement. These players will flick their wrists aggressively, hence engaging the anatomical structures that are at risk for developing RSI including the carpal tunnel, the wrist, joints, tendons, etc.
Reads as though the shorter, violent action of wrist flicking is claimed to be more damaging than constant, slower movement.