So, conclusion is, that Unknown is the most productive mangaka ever known! XD
Same thing happened to me when I was about to read this Kuroko no Basuke dj! I was scrolling through the "Other works by the same author" and then I realized it was going on forever. Though I realized that it might be "Unknown" and had a pretty good laugh when I confirmed it (with a lot of scrolling back lol)
They don't know the author's name OR they didn't write there the author's name!!
Hahaha Just now I read a yaoi manga and after this I saw that the mangaka of this manga has 423 mangas on mangago! XD now the funny part: I was scrolling threw this huge list and thought "wow! Whats the name of this cool & productiv guy?" I was scrolling back to the top and there stood......."Unknown" hahahaha of course there are some mangas on mangago where they don't know who the mangaka is ^^