I wouldn't mind adding another layer into this conversation by discussing the feet and the roles that the hip and foot action play in regards to the Pivot Train.
One of the reason why the Right Anchor, Delayed Hip Turn, Flat Left foot action should be employed because it is the ideal variation, is that if you have standard Knee, Hip action and Foot action - if the backstroke is not halted with the feet, people using this variation cannot use that same tension in the feet that halted the backstroke to launch the pivot train in the downstroke. When good golfers say they like to 'use the ground', but can't explain it, this is what they mean.
The hip action in the downstroke is very much a reaction to this. You cannot think - right, im going to slide here an inch or two and turn... The correct way is to use that tension in your feet per 7-17 to launch the pivot under your stationary head. 'Swinging from the feet' gives your stroke the maximum Swing radius.
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