I looked at the picture carefully and don't see the rear doors open. The overwing exits ARE open, and the front doors are open, but not the rear. On the side of the aircraft closest to the photographer, the raft is up against the fuselage, allowing people coming out of the overwing exits to get on the rft.

If the rear were open, they would be very obvious - if you follow the top edge of the front door back along the "US Airways" to where it would be on the rear of the a/c, you can see it's not open. The skin of the airplane is smooth there - no door sticking out a foot or so.