In Wheeljack's case, every visible panel in vehicle mode is new aside from the windshield, the part of the roof that becomes the robot chest and the tail lights. In addition, you have the new weapon and new head. Between Beast Hunters and Fall of Cybertron Sideswipe, Hasbro is on a roll with retools.
I'm thinking we're getting remolds where in previous years we would have gotten more completely new molds instead.
Its yet another cost cutting exercise.
Or look at things from the most negative standpoint... whichever.