I still think it was because there was no intro taped for DEMENTIA 13, because it wasn't part of the original lineup of movies.

I don't know when the changes were made, but DERANGED (1974) was originally scheduled for December 15 but that never aired for one reason or another. The Lon Chaney silent double feature (WEST OF ZANZIBAR/THE UNHOLY THREE) was moved up a week from the 22nd to the 15th, leaving a gap for the 22nd. TCM filled it with DEMENTIA 13. The intros were most likely taped months ago before they even knew they would end up showing DEMENTIA 13.

I fully expect Rob Zombie to be back introducing (MADHOUSE / THE LAST MAN ON PLANET EARTH) next week .