Originally Posted by Viktri
It is likely OP means OP's boyfriend's shoulders are heavily built which results in a rounded shoulder.
Agree with Viktri. I've always believed that, same as suits/sportcoats, one should fit the shoulders, neck, and arm length, and have the body and sleeves tailored. It's just part of the process of owning clothes that fit. Now then...
This is a terrible picture. I'm sure it came from a google image search, and I'm not knocking the method, just worked up about the terrible info that's out there. Big surprise that website's trying to sell something.
For those interested, the deeper muscles are stacked wrong, and the infraspinatus label is pointing to the teres minor.
Sorry about the rant, but these things are just as easy to get right as wrong.