You don't have to show me any picture I know the anatomy of the supraspinatus very well. The deltoids also origin from the clavicle and the acromion, that was my poiint. Them being strong, or whatever, just means that they stabilize and carry the majority of the load. The supraspinatus is not in a stretched position while carrying, even without abduction.
I don't agree that the position is contraindicative at all. Is there any evidence of that being the case? Do you have any clinical experience of that? Feel free to link some stuff as well, thanks.