Yes, it shows how these either/or arguments often contain hidden assumptions, or presuppositions. Thus in the Lewis trilemma, he has as one alternative, that Jesus is God. However, this ignores the point that he might have sincerely believed that, but he wasn't. And also the more subtle point that early texts don't have him saying he is God, and this is added later. So being God is imputed to him - all of this is concealed in Lewis's either/or, but Lewis is after a black and white position, in other words, a false dichotomy, trichotomy I suppose.