[Yoda]

O.B., I am finding that one of the main purposes is
to get the Right Shoulder on plane. If you do not keep
the hands and arms at the top during the shift, the
Right Shoulder does not get on plane.

If on the pivot point, the pivot/turn pulls the arms down into the ball. Any driving of the pivot with the feet/knees does not work unless your shift is completed and weight stays on the left side.

The Downstroke Pivot is characterized by On Plane Right Shoulder Turn (toward the Ball) as led by the Hip Turn (motion) and Action (work). This Pivot puts the Right Elbow On Plane, and, therefore, the Right Forearm (and #3 Presssure Point) also On Plane (pointing at the Plane Line).

All this is prelude to Release. That is, the Left Arm overtaking the Right Shoulder Turn; the Right Elbow straightening; the Left Wrist Uncocking; and the Left Hand Rolling. In other words . . .

The Pivot Delivers the Loaded Power Package (including its bent Right Elbow) to Release. Then, the independent motion of the Arms, indeed, the entire Power Package, continues that Delivery from Release (via the straightening of the Right Elbow) to the end of the Follow-through.