To really understand if hips are involved in pitching speed,control and consistency just try to pitch or hit without use it.Why pitchers and hitters underhand or overhand open their hips before push with pivot and close it following their pushing motion ?Is that simple...Why in modified fastpitch softball you have to stay square to the catcher to pitch legal?Hip is the key in throw hard especially if you throw using "across-the-body" mechanics as Bill Hillhouse teach in his dvd.
Actually Bill Hillhouse says you don't close the hips.
It's about the kinetic chain IMO not so much the degree of closure. If you don't think Ueno and Cat are using hip loading and unloading as a significant factor in the kinetic chain we see the clip differently. Even the clip of Finch shows a quick little unload of the pelvis before the arm comes through though she leaves the hip mostly open. Again, it's about energy development and delivery rather than any specific angle of the hip IMO.
Sure there maybe some movement of the hips, it varies from pitcher to pitcher, but telling a girl to close her hips can cause problems. One of things that I have been noticing at the lower levels of Division One is that many pitchers leave the hips wide open and actually bring the elbow inside the hip. With a move like that you can't close at all until well after release.