Harry Potter and the Philosopher's Stone has one of the warmest Christmas sequences in any family film: snow, a feast, presents at the foot of a bed. It opened in British cinemas in November 2001, and it has been part of a lot of family Christmases since.
The rubric asks a harder question. The Christmas chapter is one part of a school year that runs from autumn to summer, the plot does not need it, and the ending happens nowhere near December. That points towards Not really, however much it feels like Christmas.
It is the clearest case on this list for keeping Cosiness and Festive Factor apart. On the first it does well. On the second, one chapter can only carry so much.