I argue that some kind of films are not necessarily Christmas films; however, they are set around Christmas so they become films you watch around that time period.
I give you... Trading Places. A film from 1983 starring Dan Ackroyd, Eddie Murphy and Jamie Lee Curtis - what a cast! It is a film about... you guessed it... trading places. Dan's character and Eddie's character swap places and this is the plot.
Yet, this is a film I only watch around the festive period. Usually, my first watch is on November 1st because my festive period starts then (don't judge me). There is no real Christmas theme to the film except when Dan Ackroyd disguises himself as Santa Claus. If it was set at another time of year then he would be disguised as something else.
This is just a film I enjoy watching and due to not wanting to kill it at all given times of the year, I decide to kill it during my favourite time of year... Christmas!
All I'm trying to say is that... sometimes just having a little bit of the festive period in a film doesn't constitute it as a Christmas film; however, a person might have a preference to when they watch a particular film. So, it is down to the individual to decide whether a film is constituted as a Christmas film or not.