Actually it doesn't, it merely projects all genders onto the male/female plane. I don't think this is incorrect for this purpose, for instance if we consider a xenogender entirely orthogonal to the two standard basis vectors, projection onto the male/female plane yields coordinates of (0,0). It would be reductive to say that this is equivalent to other genders that map to this point, however, it still correctly yields the result of a tie. This is the natural outcome of neither player betting on a xenogender