For one thing it explains Hogan's ball position chart much more clearly. Where does it say in 1-L 5-17 that one should open their stance as the low point gets further ahead of the ball? One must infer that information themselves based on other statements.
The D-Plane is there to help discern true path as opposed to plane line for the real resultant path of the clubhead during impact. It's been a while since I've brushed up on my TGM but I pulled it out for the sections you cited and cannot find any reference to true path. Is there another location I should be looking besides 1-L 5-17?
Also, something else D-Plane explains is that straighter shots come from higher lofted clubs than longer clubs. That's something I explained in the first video cited but I do not see any such mention by Homer.
Shoot me your e-mail. I'll be happy to send you a book . . . that you can search . . . do the work for yourself . . . if you think it's screwed up . . .fine . . . clearly you and the squadron came to the party to stick your weenerz in the mashed taterz . . . you got 3 posts at this joint . . we ain't spoon feeding you . . . and tell 'em to spell my name right . . . it's Richie Cruise.