I would think that the neck block has come loose from the sides, and more than likely the transverse brace (under the top, below the fingerboard extension. This is probably more related to heat exposure than drying out. I am also a little bit surprised that a neck reset is not required, but it could be that the neck heel/neck block joint didn't heat as much as the sides and transverse brace, and so there wasn't any movement there. The guitar was probably overheated while tuned to pitch, and the heat allow the joints to fail, which let the string tension pull on the neck, loosening or breaking the transverse brace (allowing the top to dip), and with the support of the transverse brace missing, the neckblock, now being supported only by the guitar sides (and the back, but this doesn't really contribute a lot of strength in the direction of the string pull), starts to move forward, causing the cracks along the sides of the fingerboard in the top.
More than likely, the repair is consisting of moving the neck block back into position, after which the transverse brace can be re-glued or replaced. Gluing the cracks near the fingerboard can be a problem, as some of the length of the crack is either very close or covered up by the neck block. The good part is that any repair in that area can use some pretty large cleats, as they do not have any tonal effect.
Kostas