My downswing feels as if it is fully powered by leg drive or thrust. As you know, Richard feels the swing as a turn (and un-turn) initiated by the legs. He occasionally mentions that he feels the large muscles of the back coming into play. I do not claim categorically that none of my upper body muscles contract and exert effort, but it certainly feels that way. Perhaps my body is well enough trained such that I don't perceive that effort. When I set up properly and do a slow, deliberate backswing ('out' not inside), I feel I'm connected and any movement of my legs will pull everything down. This brings to mind Ben Hogan's statement in 'Five Lessons' that the first part of his downswing was a pulling of the club down to about waist level with hip action alone. If the club can be pulled that far down by the lower body, why not all the way through to impact? Heck, the last part of the downswing is wrist uncocking (loss of lead arm/club shaft angle) and is going to happen anyway.
Blake described his downswing as a "...horizontal rotating movement and it is the backswing in reverse." I interpret the 'horizontal rotating' to mean that leg energy causes the hips to slide horizontally and rotate back to their address position. I am not certain what he meant by 'downswing is the backswing in reverse'. I have my doubts that the downswing could be an exact retracing of the backswing path. For one thing, hands are closer to the body at address than at impact. Perhaps you could compare Richard's backswing and downswing paths to see how closely they match. When I was corresponding with Mindy he repeatedly told me to make sure that my trail elbow was not getting out of place (going too far back in backswing) resulting in a poor lower-upper body connection. Good luck, Jim