It seems 3 is really 9 or whatever, but there is no need to put the palm up at that time. At third is fine. I don't have time but I can post numerous pictures, and RP and BHH agree on the position. When she starts throwing movement all that goes out the window anyway. The elbow leading is the key. We are starting to see elbow pain in young players who force that palm up position for extended periods of overuse.
Again, it depends on what pitch Finch, et al are throwing. Having the palm up may hurt the rise or screw.
Palm up would be expected on the curve, which Ueno, Abbott throw a lot, so it is people mistaking those videos for FBs that kids should throw (and also getting confused about Ueno's funky endings some times).
In any case, it is a transition position, not a pose,
I could keep going....
Many wall wipers will go from 3B to Sky as they descend, as the advantage it creates is superior.