[Yoda]

I find that drawing to be very misleading as far as swing center and the left shoulder participation is conserned. The swing center should be somewhere in the back of the spine where the inclined plane intersects. The left shoulder has a rotary motion around this center axis. If the left shoulder becomes the swing center prior to impact you have a major throwaway situation. (sorry Yoda)

A rotating left shoulder that doesn't quit rotating before impact is important for proper impact lag pressure and all good things in golf.

The Left Shoulder is the Center of the Arm Swing (Left Arm-Club Radius). The Head -- or alternatively, the 'point between the shoulders' -- is the Pivot Center and thereby stabilizes the rotation of the Shoulder Turn about the spine as its axis.

It is not necessary that either Center intersect with the Inclined Plane of motion of the Sweetspot.