Okay, but I assumed from a video that you pull towards the eyes - hence the reason for using ropes, straps, or whatever will go to either side of the head. I think the rear delts are being used regardless of how you path the ROM, but another difference will be the weights used.
My rehab work is 25x3, using around 40 lbs...but if I were to seek hypertrophy for the posterior deltoids, I'd be pulling near BW with lower reps. And it would be impossible to do that rotating the humerus; you just don't have the leverage. The fists follow the same path pretty much, but the elbow position changes the way it works. With the ACL problem, I can't even do the elbows up position at all.