I don't see this argument making sense. Omega's claim reduces to neglibible chances that a choice of Defection will be advantageous for me, because Omega's claim makes it of neglible probability that either (D,C) or (C, D) will be realized. So I can only choose between the worlds of (C, C) and (D, D). Which means that the Cooperation world is advantageous, and that I should Cooperate.

In contrast, if Omega had claimed that we'd make the opposite decisions, then I'd only have to choose between the worlds of (D, C) or (C, D) -- with the worlds of (C, C) and (D, D) now having negligible probability. In which case, I should, of course, Defect.

The reasons for the correlation between me and Agent X are irrelevant when the fact of their correlation is known.