I doubt that's the case (although I could be wrong). I think that sales would pick up substantially at least during the preceeding month of a game's release, in this case since August. And I would have expected an uptick already in July. But I do agree that outlier sales continue for a while after a game is released.
Another possibility is that the "Starfield effect" is already accounted for (at least partially), meaning that Xbox sales would have been even lower if not for Starfield. But who knows.
Anyway, curious to see what happens to Xbox sales in the upcoming months.