I am certain it was originally meant to be 7/8 eps. That might explain why they're putting on the decidedly unfestive, and judging by the trailer not great, 3 part drama Sticks and Stones the week after. It certainly has the feeling of a drama sat on the shelf for a bit.
Good catch - Sticks and Stones was filmed September 2018 according to original reports
, back when it was called The Man. Can't imagine it was being filmed for a Christmas 15 months in the future at the time.
That said, I don't think X-factor would have gone alternate nights over two weeks anyway, maybe a Saturday-Saturday stripped affair. Now it's just every other night I think.