"With strong grips, this places the thrust of both the #1 and the #3 pressure points on plane so that the clubhead lag alignments are established and can be verified by the waggle and the forward press."
I was taught to go to impact fix. Then holding the back of the left arm level to the ground (making certain the left wrist is flat with the forearm), the right wrist will be bent and the shaft will be held out in front of you. From here the face can be checked. If the toe is up (taking into considerations of offset) the face is closed. If the toe is down the face is open. If the toe and the heel are level, it is square.
Duval has a shut face grip and uses an angled (leaning toward vertical) higne. Irwin has a square face grip and uses a horizontal hinge. Most of the great players (in my opinion) have used a neutral grip and horizontal hinge because of the hinges characteristics (closing with no layback.)
The seven grip types Mr. Kelley puts forth in 10-2-0 must have a use. As an instructor I change the grips of my better players so that a horizontal hinge can be employed. For others I do other things. However, I have never given anyone a 10-2-c, weak double action grip.
But Mr. Kelley says, "Don't hesitate to adjust you grip for better direction."
I understand 7-2 and the drill set forth in 6-b-3-0 but this is not unlocking the meaning of grip types.
------------------------------------------
THis brings me to something Mr. Chuck Evans has on his ebook. He is one hell of an instructor and knows his TGM. In his book he talks of placing the left hand on the club in its natural position. As it lays when your hand is simply hanging.

I just don't know. I will continue to incubate. Chime in if you want.