They probably did that on purpose, so that people who have seen the show, don't relate the two. I personally, like him as Sam, because I think it's too much of a type-cast for him to have played another guy named Dean, and while it may have made sense to those of us who worship GG, believe it or not, there are some people, only a few, mind you,*gasps* that don't watch GG and wouldn't even think to put the two together, so it helps to futher separate the two, which is what I think they want.