Yeah I should be a little more thorough when describing some move. Usually I just type whatever comes to mind.
When I dingle the arm in a pendulum movement my back leg gest loaded southwards against the sideways movement by my arm. I almost want to unload that tension against the instep of my drive leg and start going towards the target again.
When doing the same perpetual motion drill with the full windmill arm movement I noticed that my drive leg gets loaded differently. Firstly I get some vertical load on it which then translate into lateral movement northwards to the target.
So the difference is: pendulum - sideways loading & windmill - vertical loading.
Oh gotcha, and no worries, I'm just as likely to be unclear in writing most of the time lmao.
Incidentally this is related to & reminds me of the thighmaster/adduction chatter on the other thread. I find this easier to notice and manipulate in standstills, and since my drive leg is weaker (physically) and gimpier than my plant leg I was stopping to pay more attention to the moves again today and realizing it was probably at least part of why I always have trouble getting complete balanced stability in transition. If not a literal Thighmaster I should be doing a bit more hip adduction exercises than I have recently lol.
Yes, I think the pendulum will tend to coil back more south with more horizontal force in general, which will also tend to get you more athletic load and tension "sideways" engaging that hip adduction effect. That's part of what ideally is stabilizing your balance when you walk or run etc, you just do less of it when walking forward.
When I do either standstill full arm windmill or full x-step windmill, like you I too tend to get more vertical load that moves me northward toward the target. That's a potential source of power. However:
I think the tricky thing we were talking about above is what's "best" or finding a "sweet spot." For me or other people I work with, you've got a lot of theoretical options going into the reachback or backswing that are all "acceptable." My own pendulum has always seemed to work "best" when there's a clear phenomenon on the drive side - I need just enough verticality to feel deweighted and "levitated" briefly in the backswing at least so I don't get stuck on the drive foot (athletic walk, run, hop etc). I also need to get juuuuust the right force moving back opposite my shift to get that athletic loading in the core, which seems like 25% of my power (I'm guessing of course, but you get the idea).
So what the windmill helps me (or others) access is that "levitating" part by carrying me
all the way off the ground vertically briefly. Because it's circular, it also taps the natural way the hips work in transition like Swivel Stairs. Like, alarmingly well for me, and I've now seen it give a lot of players "ah ha! -s".
But like anything sweet, you can spoil your meal, so beware.
Gurthie seems like the closest modern thrower to a pure windmill and I would still call his move a form of windmill like Sidewinder does, but even though he's got a very centrifugal move, his backswing is still working a lot like a pendulum arc in transition, so that he is getting enough of that leverage you can find in a pendulum. I've also found it sort of interesting that my own X-step move is gradually evolving from having a lowish backswing like Gannon Buhr or Aderhold to a higher "levitated" backswing like GG. I didn't really do it on purpose but as I kept working on my balance it gradually starting happening on its own & is directly related to a better effort/distance ratio in my case.
I still use a low backswing for a lot of standstill shots depending on the shot, and I think especially high trajectory hyzers on rough ground where I need very sure footing from the rear leg.