In fact, Harry and Quirrell agreed with each other that the original Horcrux did not work because it did not preserve new memories and so did not have true continuity of self. If this was right, then Harry just (in effect) murdered Draco and revived him with a Horcrux V. 1.0. And even if it isn’t right, Harry should think that it is, according to his discussion with Quirrell.
In fact, Harry and Quirrell agreed with each other that the original Horcrux did not work because it did not preserve new memories and so did not have true continuity of self. If this was right, then Harry just (in effect) murdered Draco and revived him with a Horcrux V. 1.0. And even if it isn’t right, Harry should think that it is, according to his discussion with Quirrell.