Not sure how to reply to you and keep all your imbedded comments sorry.
TM seems to me to show staying on backside and barely touching front leg, so more over backside. I have tried to watch alot of his stuff, but it is hard to get thru alot of times. STuck back to me i get, i think, which is why i like the dynamic balance theory, i do however believe in more of a 60/40 to backside. I think it is the only way to get the correct tilt and body posture. Otherwise you stand more vertical (from a side view at least)
'But the pivot is occurring as that movement occurs.' Agreed, i had some prior comments about the wrist supination in another thread, and am not sure yet, depending on the barrel starting point, whether there is much supination. i would think there is less in the neck slot, but in an any case goes along with palm up palm down. This is probable where i am telling my DD to try and tilt properly and feel the 'Swing Down' to the ball and keep barrel angle the same as shoulder angle.
Agreed on the many definitions, and that is where the problem starts for me. We started to literally torque the hands like ™ and got severe barrel dump. Now i see it as more keeping the tight pivot point, to 'stay connected' and stay on angle with tilt at launch, swinging down and to the ball. I can see where it can help, but it seems easy to overcoach that aspect of it like i did.
Some of TM's demos are exaggerated. He is performing an action without including other parts of the swing. So it can be a little tricky. In general he promotes two engines. The rear hip pivot point and the hand pivot point. Both need to work together, otherwise the results will not be there. If a hitter does not get the lower body part correct, barrel dump could be a result. I agree with your 60/40 for the most part... There is some variation.