Has he not located the Turned Shoulder Plane with both the Club and his hands in Frame #4???...Perhaps I'm not reading your point correctly!!!! He just locates the Turned Shoulder Plane as a result of over-lengthening his stroke via a double shift...If he hits Cut shots I've seen him use Single Shift...rather than the pics posted here...I'll try to post some different pics of him using a different procedure....For Comparison!!!
I think the primary benefit is Maximum participation and Range of Motion of the Power Package Components are utlized which gives perhaps better performance characteristics of the other Plane Angles and their Variations...
Your comment from an earlier post "not on-plane but...Parallel to the Elbow Plane" I think is sufficient for me at this time. I can't however read much encouragement for turning off plane in Mr. Kelley's 10-13-B/C comments. Of course, there is ample support among prominent instructors and players for a shoulder turn that extends beyond the plane line and for different combinations of up and down shaft planes. It would be interesting to know if Mac reaches the TSP by default or intent.... does he think in terms of having the lead arm and shaft at the top on/parallel to the plane the shoulderS turn on, or on "reaching the TSP."