... Perhaps, but that's no longer isomorphic to the actual problem. We are past the point of Omega's influence; in Newcomb's problem, it'd be as if Omega grabbed your mind state, ran it forward until it confirmed that you would not initially two-box, and then stopped. Omega itself has been removed from the problem, and you're left with one empty box that you've already claimed a million dollars from (or negative one million, in this case) and one closed box.

Near as we can tell, history can't change in the MoRverse: what's done is done, so Harry might as well exploit it.