There wasn't any discussion about this one? I'm surprised. This rename was brought up in a past discussion.
I ended up being against it because people pointed out the Roaring Knight should be the article name if the Man was moved to Forgotten Man, but I disagreed since SuperFeatherYoshi found out there is a special Japanese translation for the Knight. Not only that, F-sharp brought up that "man" is used more, which aligns with our current Manual of Style for canon names: the most common name is prioritized, like Dess and Rudy.
Also it would go against the deltarune.com URL for /man.