Correct. However, a well functioning shoulder is a pretty complex mechanism. If any part of it is removed,the others struggle or fail altogether. A removal of t

Correct. However, a well functioning shoulder is a pretty complex mechanism. If any part of it is removed,the others struggle or fail altogether. A removal of the entire arm, offloads all the work onto the edge of a shoulder that would normally receive help from the arm and its connected muscles. I did break humerus in my left arm,which resulted in functional degradation of my arm: I can't lift heavier things in a certain way, some movements are restricted, the arm gets stiff if I sleep on it,etc.) All in all it's not too bad but that's the result of some muscle damage,so try to imagine how bad it is when the whole arm is missing.