[Mike O]

A lot of good thoughts here:
Leo, absolutely a big change- and nice job questioning the reasons behind it- it deserves that kind of questioning.

I also think that Lynn was correct in explaining why the change was made- and I do think that Homer was telling you the rationale for changing it as quoted.

You might think of it like this- as noted in the 6th edition 2-G. The Geometry of hinging is clubface control- The Physics of Hinging is that Hinge Action is the result of the turning torso or orbiting arms. So he's given Physics the nod over the Geometry in regards to it's categorization in Zone#2 as opposed to the 6th edition in Zone #3. Why?

It's been 24 years since I learned of the coming change of Hinge Action from Zone#3 to #2. And I had the feeling of - "What - how could he do that!!!"- because it does really create a mental shuffle for you and everything that you've learned. I asked "Why would he do that?" And the answer that I got was "You see- everybody thinks that hinge action is something you do with your hands- and IT'S NOT!" Hence, the categorization change to move it into a category that better categorizes the component in relation to the procedural nature of the movement.

As far as the integration of concepts in the book for clarity- that's been a problem from day one. And as Lynn points out - continues to be a major flaw that doesn't help anyone. Woulda, Coulda, Shoulda in the 7th edition, but there was no way- that was going to be Mr. Kelley's 7th edition and no one elses. Those changes are needed but would have to be in the 8th edition- and if the 7th took about 24 years to publish then I guess the 8th could take over 100 years to publish.