[Daryl]

If you adhere to the "Power Package" theory, then the answer rests with the Alignments and assembly of the Power Package. Flat Left Wrist, Bent Right Wrist, Left Arm Wedge, Right Arm Wedge, and Left Arm and Right Forearm Wedges Aligned 90 degrees to each other. Release occurs while the Right Arm is Straightening without Changing those Alignments (Including Putting).

Given a parallel Stance, Plane and Target Line, then:

Single Wrist Action, Aligns the Power Package by the End of Start-up. These Alignments remain undisturbed until Both Arms become Straight during Follow-Through.

Standard Wrist Action Aligns the Power Package by the Beginning of the Backstroke. These Alignments remain undisturbed until Both Arms become Straight during Follow-Through.

Double Wrist Action Aligns the Power Package one Split Second before Impact. These Alignments remain undisturbed until Both Arms become Straight during Follow-Through.