[Daryl]

The way I explain McKenzie's results in every terms is that as the club is set (at transition) under the plane where the hands will move, the dragging from the hand will tend to move it back to the plane. This produces the supination of the left forearm and, if everything is time perfectly, the squaring of the clubface.
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Thank you for the clarification. I don't know McKenzie's work. Forgive me for this long-winded post. It's been awhile. But hopefully you can get through this. This is so much easier to explain by "show and tell" video.

In "Golfing Machine" terms, you're describing the "Flip Release" on the Elbow Plane.

At the End of the Backstroke, when using a Shoulder Turn Takeaway, the Right Forearm has "Rotated". This results in the Right Forearm Flying Wedge being woefully misaligned to its Impact Alignment.

Now, imagine the Elbow Plane. At the End of the Backstroke, the Hands are well above the Plane. Somehow, the Hands must get down to the Elbow Plane for Impact.

Now imagine Sergio Garcia. At the End of his Backstroke, everything looks seemingly perfect. But, as he transitions to the Downstroke, his Right Forearm (look at his right Wrist), remains "Rotated". So his Right Forearm looks kind of parallel to the ground while his Clubshaft is almost vertical (on-plane and perpendicular to the base line). To most everyone, this looks normal because the Clubshaft is perfectly On-Plane. But the Clubshaft is not aligned to the Right Forearm. He must (compensation) "counter-rotate" (Clock-wise rotation) the Right Wrist so that the "Right Forearm Wedge" is On-Plane at Impact (Flip Release).

When you use the Elbow Plane, its very apparent, as you have pointed out, that the Right Forearm Wedge alignment is NOT in-line with its movement-direction (path). But this is how the Right Forearm Wedge operates. If it were in-line with its path, it would be "Right Arm Swinging".

It is true that "Dragging the Handle" will cause the Clubhead to get in-line (from being off-plane) with the Hand Path. But this also causes the "Counter-rotation" and re-aligns the Right Forearm Wedge for Impact. Dragging does not cause Release (the Pulley).

The problem is perception. If this occurs "early", at Transition, it appears that the Club was laid-off. If it occurs "Late", you think that Dragging the Club has Rotated (counter-clockwise) the Left Arm. Actually, its the Right Forearm Wedge that rotated the Left Arm.

This total concept stems from the Right Wrist Rotation at the End of the Backstroke, caused by the Shoulder Turn Takeaway. If this model is considered "normal" and is used to examine the Golf Stroke, keep in mind that you are examining a compensation.

All of this lead McKenzie to "Think" of "passive rotation". That's a giant leap. He ended up at the right place while going the wrong way. If he continues this research I think that he'll discover that the Pivot Rotation and Arm Motion truly square the clubface for impact without any need to apply torque to the Clubshaft.