The thought of them having both MCR and Green Day in the same year is mad. Two of the biggest bookings they could make. If MCR are sticking around, it could work out better in the long run not having them in the same year and they can spread them out over multiple festivals.
Well, moreso initially that they were cheap to offset MCR + Green day or Muse + Green Day or whatever. Then rather than dumping them they're just giving them the spot anyway and either pocketing the change or spending it on a bigger undercard.