No, I'm not. All of these are, to the extent we know about them at all (which in some cases we don't know much), entirely unlike any Christmas traditions we have today which are claimed to be pagan in origin.
In the absence of evidence about the timing being affected by other festivals and in the presence of much evidence that all the actual traditions are far more recent than pagan, I don't believe it's fair to claim Christmas has pagan origins. The absolute best we can do is say that its timing may have been influenced by other, pre-Christian celebrations.
Here's another one on Saturnalia from the same scholar:
Later during Soviet times secularish Christmas traditions including Ded Moroz were moved to New Year's.