Like others have already said, I'm not sure why some of these weren't on the album. Maybe someone at AP could reach out to the band and ask them (I'd like to hear their take, maybe the label wanted a short album). I can understand a couple of b-sides, but six from an album made up of ten songs is nuts.
If the album had 12 or 13 tracks, the 6 b sides would be more believable. Especially since they've been working on this album for a couple of years. There's a whole bunch of music artist that do that too.
It would've been nice if they added 2 or 3 more songs to the official tracklisting