Likely wasn't finished in time. During early 1984, Michael was playing the song for people to get the hype going for Victory but probably pulled the song back because he felt it was too good to be on Victory and chose to save it for Bad. Even though the brothers provided background vocals, it was probably to flesh out the chorus but with them already being in the studio, I don't see why it would hurt to have them do it.
He submitted 5 songs, assuming they were Be Not Always, Buffalo Bill, Liberian Girl, State of Shock and probably Dream Away as Toto was scheduled to co-produce the album.