Can't shorter players can spin faster than taller players? Wouldn't this--at least partially--negate the height issue?
I'm not suggesting making this some sort of hard and fast rule where I would expect people to call "the" on someone mid-string after setting a little high on a spin. All I'm really trying to accomplish is to explore the idea a little bit in the interest of better defining what is the most efficient and technically valid method of hitting spinning moves.
Anecdotally, spins feel the most controlled and easy for me when I keep the set at about eye level. When I set significantly above this area, I find that the bag starts to travel faster on the down-stroke; this speed gain might actually negate the extra time that you get by setting high on the up-stroke. This also makes it potentially more (unnecessarily) difficult to stall as an added side-effect of the speed; I find this particularly true of the smaller, heavier bags that have become standard.
Perhaps maybe why my statement rings true to at least a few others is that it actually is true for spin
sets, and maybe not for complete spinning moves. In other words, to do a spinning > inspinning osis ("double spinning osis"), if the first spin goes above your head before you spot the bag, then the move becomes a "true" double spinning osis, where there is a set, and then two spins, then the osis. If you're spotting the bag on the way up, then it becomes a spin-set, and is technically a different move than it's "full double spin" cousin. This is maybe why the "if you don't spot on a peak" statement is true too.
Now I feel like I'm starting to over-analyze

I accept that my whole statement could be bunk. It just seems to make some sense to me that is hard to define.