Looks to me like the sculpt wouldn't allow for him to wear the glasses correctly without modding the sunglasses. But personally I prefer it that way. If they stuck little indentions/holes in his hair, it would detract from the sculpt when he wasn't wearing them. Which he won't at all for the vast majority of collectors (he only wore them briefly in the film--in that scene with the yellow guitar we aren't getting--and didn't wear them even in that poster). All you would need to do is trim the glasses arms a bit, and maybe use a little dab of sticky tac to get them to look good wearing them.