My hunch is that the mold they used for the DX Rocs has a 1 degree draft. That's really about as little draft as you want in a high volume mold.
I would have expected closer to two because of the longevity issues you mentioned.
EDIT: Stardoggy, if you don't mind me asking, what's your connection to the injection molding world?
I work for a large bathing company, and design plastic parts for a living.
I give *doggy's mom so much injection. hot. beef. injection.
Yeah right. She only likes red meat, not tuna cans.