Root and back foot,
I am going to play politician here and be on both sides of the debate! If you think of it like a coil spring that is already rotating then the coil is sprung loose in the same direction would not both activities be miltipliers of velocity? Not sure to be honest but it seems to be intuitive to me. But root I feel your pain. I don't think it is so easy to get hs pitchers to execute separation. And for those who really struggle with it I think your early hip opening may be a good idea as long as their lead foot remains linear and the shoulders don't open early. Better to have one velocity multiplier than none. And maybe by doing this for a while they would eventually gravitate to a more sequencial firing of hips then shoulders. Kind of a walk before you run thing