[Yoda]

If the left wrist is flat level and vertical, and the right wrist is bent level and vertical at impact fix, is the cocking of the left wrist solely due to the bending of the right elbow, maintaining the right wrist in the same bent, level and vertical position that it was at impact fix?

For Hitters -- that would be you, JG33! -- the Right Elbow does indeed Cock the Left Wrist as it Bends and Fans in the Backstroke. But remember, the Hitter's Left Wrist Action to The Top is essentially Angled Hinge Action (10-18-C-2). So, while the Right Wrist retains its Bent (Horizontal Grip Motion) and Level (Vertical Wrist Motion) Impact Fix alignments, it continuously Turns (Rotational Hand Motion) from Start Up to The Top. Study 4-0.

The Golfing Machine. Gotta love it!