[Dovecot] convert plugin created maildirfolder file in root maildir directory

I've noticed that if a user's maildir gets created by deliver or pop/imap without the convert plugin running, the maildir structure is fine (no maildirfolder file). But, if a user gets converted, there is a maildirfolder file in the user's base maildir directory. As far as I can tell, that doesn't cause any problems, but I just wanted to mention it. I've looked at the code for a while but didn't find why it behaves differently.