Yes. That allows the upper bunk/backrest to conform to the curvature of the front shell when in sofa mode. It is a critical design element. (Eddie - I'm curious, because I've never taken mine apart… how are the two plywood wings attached to the large piece? I can't see anything in your picture.)
And Bill, you are correct, there is a hinge that attaches the bunk to the ledge under the front window. It's an offset hinge and it isn't in the pictures because you wouldn't attach it until the cover is on and the whole thing set in place. The bunk rests on top of the ledge, which carries the weight
, and the hinge is attached to the bottom of the bunk and the underside of the ledge. I can post a close-up picture of the hinge attachment later today if you'd like.