Oh, so i was right in assuming that you actually thought that he made the HE Grenade
Because what i assume is Ephialtes' shotgun is also on that list, as well as RTB, the New Duplicator, the Fill Can, and the P90, all of which i don't recall Hata having any involvement in the creation of, then there's Drop Items On Death, Footsteps, Hit Location, Physics Death, the Music Player, and Trueno's colorset, but i'm less sure about Hata's involvement with those than the others
So to say that these are "Hata's add-ons", isn't entirely true, and kind of loosely phrased for add-ons where he just tacked on some additional code...