I know where you're coming from and I agree that teachers fall into patterns.
Lynn told me, and I agree, and Homer said this in the book, that the Left Wrist can either Face the Angle of Approach or become perfectly Vertical at Impact (Sorry, I don't have time to look it up). Could that be the difference?? Could a Left Wrist Facing the Angle of Approach lead to a naturally occurring Bent Left/Flat Right Wrist at Follow through? And, one that's perfectly Vertical lead to keeping the Right Wrist Bent? I'll experiment over the weekend.
When I use: (all 3 Patterns include a Flat, Level and Vertical Left Wrist at Impact)
Bent Left at End with #2 PP Sensing Lag: Flat Left Wrist Finish Swivel. When I just want to enjoy the Play.
Flat Left at End with #2 PP Sensing Lag: Flat Left Wrist Finish Swivel. I don't use this very much. Very difficult.
Flat Left at End with 3# PP Sensing Lag: Flat Left Wrist Finish Swivel. My Favorite.
Ive highlighted a sentence above. Maybe its a typo , not sure but Lynn teaches Impact Hands at Follow Through. Flat Left / Bent Right . Not overly arched or anything else. Then bent left / flat right at Finish Swivel. Like a mirror image of the backswing . Two halves making a whole. An unbridled flail action , a release of the right hand bend if you will.
But again IMO "Flat" is not necessarily visually "flat" . And so there is often a little bend to the left wrist at Top even though its said to be Flat. This is also what he teaches IMO. Well I know for a fact . We discussed this point both in person and via email .