Anything on a mannequin, or catalogue/posed photo for that matter, can be made to look very different from how it will actually wear. I'm not saying that one won't have some structure, but the mannequin picture is no guarantee... There is nothing stopping the photographer from putting some padding on those shoulders.
As I have learned from some ill-advised eBay purchases... It's easy to pin a garment to give it some shape and structure when it only needs to look good from one angle.