Shoulder Turn Throw versus the Wrist Throw

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Spent several hours at the TPC Norton range on Sunday and TW has the tighest dispersion of anyone out there. His swing is tight, controlled and powerful low draws. He was practicing a very odd movement. He would rehearse his take away to the top then pump drill down. During the pump drill he was purposely bending his left wrist and flattening/arching the right wrist as much as humanely possible. All I could think is that he is trying to rid himself of the arched left wrist at impact??