I am not an anatomy expert, but I think there is also a shorter muscle above the clavicula, that looks like an extension of the shoulder muscle. If I remember correctly, one is for lifting the upper arm to the side, while the short one is to move the clavicula upwards towards the ears. And it's not the green neck muscle, that one is for moving the head to the side.
The important thing, on a really shredded shoulder, the muscle doesnt stop underneath the clavicula.
https://tse4.mm.bing.net/th?id=OIP.hw7_Suxf-xoHOE96qUKVnQHaEK&pid=Api
checking, if the link works