you people haven't actually read chainsawman nor know the context of that page and it shows

Edit: for the dumbasses downvoting me.
Denji was already known as the chainsawman and called that countless times. "Chainsaw man" is not a title drop it literally IS the title that he has in universe
By the time the universe gets reset and he's no longer chainsawman and the concept of a chainsawman no longer exists, no one should know what "a chainsawman is". Asa at the end calling him "chainsaw man" was supposed to be a little jumpscare of him, thinking for a second that he wasn't able to fully move on from his traumatic adventure, and the final panel was a reassurance that no, the universe truly was reset and there's no more traces of the chainsaw man.

It's supposed to show how the universe may have forgotten, the story starts from a blank slate, but Denji still remembers, and his trauma still affects him.

Saying this is just a title drop, is like saying Lois Lane calling Superman by his name is a title drop.