This is getting fun...mainly because we are able to share experiences, ideas, and knowledge, even if we don't completely agree, don't agree at all, or find different ways to get there.
Root - I think when you state "hurdling" you are talking about the front leg swinging open to get the hips square to the target, correct? If so, I am not sure I agree that it does not matter how you square the hips to HP, I believe you want a "swinging gate", and not a "revolving door". I have always said, the lower half mechanics are very similar in pitching as it is to hitting. You want a firm / somewhat closed off front side, to rotate the back side around. If you rotate the entire piece, sure you ensure complete "squaring" to the target, however I don't think you create the "elastic energy" between the top / and lower half....at least not the same as if your "firing" mechanism is the back hip being the dominant rotating component.
Each sequence influences the next, and I don't think they are completely static & segmented movements, they influence, and hopefully make the next sequence more powerful. Otherwise, why not have the old "Mike Marshal" delivery where you step towards the plate square from the "get go" without ever going sideways. I hear your statement on the slingshot, however I will ask if this is the case in pitching, and hitting, why not just hold the bat in the "power slot" then swing, and not have any gained momentum from let's say a "tip & rip" style of hitter (i.e. Gary Sheffield)?
Jolietboy - not a fan of Brent P...., and I would not construe BOF or any others as argumentative....I think your topic has yielded a great discussion.