I think we're saying the same thing here maybe cause that only happens when their both on the same plane, ie when the Right Shoulder is on the Inclined Plane in Startdown (TSP by definition). Startdown the period of Shoulder of Acceleration by definition. Hands are always on the Inclined Plane , if the Right Shoulders gets on it too at Top...you got a TSP angle of which there is a range I suppose.
I tried doing a few drawings, when you get into all the parameters , TSP, Flat vs Rotated , zero or single or double shift.......it gets messy. Need to do them to proper scale to make the implications to shaft angle at impact, waste bend clear and relevant. Hard to do on the beach.... But they would describe TGM's Standard Shoulder Turn , S and T Rotated/? Double Shift and I was looking at Matt Kuchar there in pencil form too on one of them.
Im thinking this'd be a good thing to doodle out .....the photos in the book are great but some simple stick men that would also combine the various related components (TSP, Standard Shoulder Turn, Zero Shift or minimal a shift) would make for a nice presentation of one of Homers most brilliant ideas....... Maybe we could Yoda to offer an opinion to make sure we're book compliant. One thing though .....I dont think you can do it with a hanky under your arms. You need independent arm motion (independent of the PIvot).
In any event .....Why is the Alignment Golf Shoulder Turn "Flat" on the backswing (only, not on the way down)? To try to get the Right Shoulder over to the Elbow Plane or as close to it as is possible. So as not to necessitate a shift of any large degree during the Downswing. Final final answer. And of note. Just because the Right Shoulder turns Flat does not mean the Hands are going back flat given Independent Arm Motion. A free connection where the Arms meet the Shoulders (Pivot). Right Shoulder turns IN, Hands go UP , but they meet up on a TSP and share a ride down the Inclined Plane..
I keep saying that bit.....its the brilliant result of these component combinations, this pattern. Genius. That or Im totally crazy.....or both I suppose, if you want to catalogue all the possibilities , Homer would.
Homer listed TSP for the Plane Angle, Zero Shift and Standard Shoulder turn for both Basic Patterns of 12-1 and 2. You can argue whether Zero is really possible but assuming minimal shift as a goal anyways ........He was clear in his preferences and from my experience Id have to say he's correct. Very correct. But not commonly understood maybe? Its too bad, it'd be revolutionary and its already 40 years old. That said you do have options.....not saying Double Shift is not workable.
The downstroke subject is moving well beyond the Back-stroke question this thread is based on. Therefore, and also because I have learned over time that any perception of challenge to established dogma never has a good end. Perhaps, we can return to it at a different time in another, more appropriate thread.