User blog comment:Jrotc193/Behind the Scene/@comment-79.176.247.207-20121203043324/@comment-972068-20121204070914

Because he's in a movie not written by Oda. Strong World was written by him, also he's pretty much implied that it's part of the series, so it's more-or-less canon.

He is Executive Producer in this film, though. That job is much more important than writer.