This is true this is true...
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Look at the pic of a Double Shift or Single Shift in TGM....if you have the book...
The hands go to the inside (i.e. under the Turned Shoulder Plane) until about halfway back....when they are done that route (you can only go inside so much....i.e. whe the right elbow has stopped folding, the right arm will want to lift the club to the TSP) they start going up towards the TSPlane.
Check VJ:
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Can you see what it would look like if VJ stopped his backswing short of where he did? Now envision it stopped short, with enough wristcock to make the shaft parallel to the ground (without Double-Cocking, most people will never come close to being able to do that with a short backswing)....
Can you see how this creates the illusion of a "full" swing?