Yes and no. He is Magus in body as but in mind no he is his own man. If this engima happened to be future Magus then he would remember nothing, so there is no conflict in the story. What if a memory wipe was just that a removal, destruction, not just hiding them or changing them. His body lived, but he died.
If a new game was to surface and explain Magus, how tragic it would be if this, for lack of a better word, random traveler is the "fiendlord" and never did and never will know it. In fact CC did a great job at making him NOT Magus, but Guile