Why The Change on Elbow Plane to Turned Shoulder

[12 piece bucket]

Question 'bout a Plane "shift" . . . .

In the 3rd edition Homer seemed to have a liking of the Elbow Plane vs. the Turned Shoulder. Check out the descriptions below . . .

10-6-A. ELBOW Wher the Right Elbow touches the waist is the reference point used for this Plane Angle. It is the "flattest" normal Plane that will still allow the Right Forearm to to be On Plane during Impact. This means that normally the Right Forearm will be moving at right angles to the torso - which are the unexcelled alignments for Right Forearm Power and Control.
Remember - the Right Forearm cannot become "On Plane" until the Right Elbow becomes "On Plane."

He didn't give much on the Turned Shoulder Plane in the 3rd . . .

10-6-B. TURNED SHOULDER This reference point is primarly the point reached by the Right Shoulder after a Flat Backstroke Shoulder Turn. But any other controlled Shoulder Turn can also provide an acceptable reference point. See 10-13-0.

But in the 7th Homer seems to "shift" his favorite Plane . . . .

10-6-A ELBOW Where the Right Elbow touches the waist is the reference point used for this Plane Angle. It is the “flattest” normal Plane that will still allow the Right Forearm to be On Plane during Impact. This should produce a very flat Angle of Attack (2-B) with reduced Backspin and should be avoided for Short Shots unless it is also part of your Full Stroke Pattern. The Elbow Plane allows maximum #3 Accumulator requiring earlier Release per 6-N-0. This procedure is executed by the Right Forearm per 7-3 and 10-6-B and Elbow Location per 6-B-3-0-1.

10-6-B TURNED SHOULDER This reference point is primarily the point reached by the Right Shoulder after a Flat Backstroke Shoulder Turn. But any other controlled Shoulder Turn can also provide an acceptable reference point. See 10-13-0. This Plane Angle has far better performance characteristics than any other because any Plane Angle Shift is very hazardous. This procedure does not refer to the disruptive Shoulder Turn Takeaway – which is always too “Flat” and/or too “Low” making a Plane Angle Shift mandatory and usually unintentional and unsuspected. Study 7-3 and 10-24-F.

Is he saying that due to the Shoulder Turn requirements of the Elbow Plane that there is a manditory Shift in the Plane Angle?

What was the reasoning for the elimination of the stuff about the Right Fo'arm moving at 90 degrees to the torso?

Also why would the Elbow Plane reduce backspin?