Correct! Not "all the ladies" have the thumb in by 9:00, just like not "all the ladies use a backswing" in the pitching motion. That's just the training goal I use to KILL I/R IN TIME no matter what kind of change it is.......And from experience that goal works to shut down I/R without slowing down the arm circle..........
Doesn't mean you have to teach it that way.......You need to find what works for your DD.
From my experience, attempting to turn the thumb in "just before release", you risk adding velocity from I/R that late.......
Something like this is my is what I advocate........Certainly LONG before "almost at release".
Shove it.....Flip it......Pull it.......Kill it......JUST DON'T THROW IT...........
Ok...Im on the right path in my understanding of your posts!
Thank you this helps a lot!