It happens during the build process. If the gel coat or the skin coat is to thin or hot or does not have a consistent thickness it can lift from the mold it will look "warped". If the gel coat sits to long before the skin the same thing can happen. Most will notice the wave or warped look in the outside rear of the ski. That is because it is hard to spray the gel coat in that area of the mold and the gel coat will not have a uniform thickness.
From my experience you are describing Pre-release of the gel coat. It is true the rear tray areas are hard to spray but an experienced gel coat sprayer knows how to overcome this. That is not happening to these superjets.
Most skis come fairly straight from the dealer. As time goes on the foam shrinks and the fiberglass has no where to go. These sides are very thin and partially rely on the foam for support. As you notice the bulkhead almost always prints through. This may be influenced by your climate, pressure changes inside the tray, water intrusion, and use of the ski.
In fiberglass laminating there is a problem called the Oil-can effect (old term). On larger flat surfaces a slight inward warpage can occur. That's why you try to put a slight arc to most visible areas. If the original builder of the plug for the superjet would have did this to rear areas this possibly would have lessened the chance of it occurring later on. Kinda like making something wrong to make it right....
