I’m not sure if we’re talking about the same thing. If you let your arm drop with a weight in it, wouldn’t the stopping point be where it slaps against your thigh?
Reading back to your opening post, I still think your stopping point as described there would be the point where the force gravity exerts on your arm stops being greater than the stretch-inertia your muscles exert on it in a relaxed state.
“When I see weight lifters on television lifting really heavy weights, there are one or two resting places where they pause before lifting the weight over their heads.”
You mean like this?
I think that’s a matter of completely different things. This guy brings the barbell up in one swing, then pauses for a bit, then presses it over his head in another motion. Between the first and second movement, he needs to get his arms from above the bar to below the bar. Before he’s done this he can’t direct his force properly to get the barbell further up.
The “stopping point” in your arm lowering experiment is completely different from the “stopping point” in a clean&press.
For that matter, I’m pretty convinced your unified “stopping point” concept doesn’t really exist as such. When you lower your arm, the “stopping point” will vary based on muscle fatigue. There’s no anatomical significance to this position.
When you throw a ball, the various part of your arm don’t stop moving where they do because they reach a “stopping point”, but because the muscles are coordinated to work together as effectively as possible, and while some could move further that would make the throw less strong.
The stopping points of an elbow will just be the point where the joint won’t move further (which is a property of the joint) and the point where the lower arm bumps into the upper arm.
You will also find a “stopping point” in your legs when you try for example to do a split, but that in turn is because the maximum length of your leg muscles is finite and won’t stretch beyond a certain point.
It seems you’re looking for one single anatomical explanation for resembling but fundamentally disparate phenomena. There is no such thing. Each kind of stopping point has its own explanation.