I will point out this important matter later.
After testing several graphic reproductions, I resolved to rely on radiographs, certainly not all the same, but not invented. Some are very responsive, thus confirming what I have described. But considering for a while just one pictorial theme, the superimposed dark image may be questionable due to the lacking length of the arms (longer and shorter ones exist), but proves to have respected the length of the limbs in their angles of rotation. A silent message?
It should begun to be noted that when the arm is rotated upwards, the articulation fulcrum is also raised.