Word for stating something as fact when narrator and audience knows it is untrue?

I am looking for a literary term that is similar to irony. Basically, the narrator say something in an almost sarcastic way by stating something that everyone knows is untrue. The quote I am going off of is “…nothing mattered except that Lupin stop pretending that Sirius, who was standing feet from them behind that old curtain, was not going to emerge at any moment…”

Sirius of course has just died, and the narrator says that he is “standing feet from them behind that old curtain” when everyone knows that is simply not true. Is this some type of irony? Rhetorical statement? I need to know!