My guess is the roll got crushed at some point.
Making aluminum balls is a thing people do. If you hammer the ball on an anvil over and over as you add layers, it almost fuse-welds itself into a solid block. It isn’t actually solid aluminum, but it starts to act like it. The outer layers behave just as you describe- you can pick off little pieces, but the sheets have lost all separation. So maybe if the roll got crushed under a pallet or something before being put in the box, it would do that.
