I believe Oliver Stone re-wrote the screenplay so much that it was a vastly different story. The original draft was much closer to Howard's Conan, but Stone made it the movie we know. (And, admitably love.)
I think I learned this while watching the limited edition DVD with the comentarries. It is a must watch, Arnold's comentary is hillarious, "So ya, this is good part, see here I hit him and he falls down."