From your contribution, it is clear that you are either much more knowledgeable about the golf swing than I am, or much smarter (I assure you that I'm not being sarcastic). I bought TGM in 1980, and spent many hours in the next couple of years trying to figure out what Mr. Kelly was trying to say. I think that I learned some things from the book, but its structure was infuriating.
I have come to three conclusions about this book:
(1) This book can be of no help to the vast majority of golfers, including low handicap amateurs and professionals
(2) Mr. Kelly's mechanical analysis of the components of the swing are probably largely accurate, but I suspect that it is not totally accurate (and no, I can't say what is wrong)
(3) Mr. Kelly would have needed a very good and knowledgeable editor if he wanted TGM to be any more than a major curiosity in golfing literature