I was aware that Allen's position was a bit 'worse' then the two pros and your point about the trail hand is a good one. I was trying to show that there are different release mechanisms among fine golf swings. As you mentioned the most absolute seems to be the y impact position. There does seem to be some variation after that.
I think that if the lead hand grip is stronger then the Y will tend to be in place well after impact as the tendency is to hit an hold.
Anyway I wonder if it is a good idea with IMA to keep the trail wrist bent after impact? Possibly not as Scott makes it clear that both hands should go to straight.