She had told the princesses that Sombra was seemingly insane, had lost his memory, and had developed an entirely new personality, but not much else. An outside observer might call this a tremendous oversight, but from her perspective that whole ‘human’ matter was just icing on the crazy-cake, an inconsequential detail to a much grander issue. So, when she summarized events for Celestia, that inconsequential detail got axed. 