Well this is odd. I wonder if GS reprinted Dragon Quest IV. Before this restock only 4 stores had copies. Now,almost every store in Phoenix has one. With packaging is a different story.
I absolutely hate GameStop's disc/cart-only reprints. Cave Story 3D and Dokapon Kingdom will never be CIB in my collection, and I hate that.
Every GameStop around me has at least a copy of DQ4, so you might be right about something weird going on. My guess is that this isn't a real reprint just like the Nier restock, but rather just a bunch of old stock being sent to stores.
Wouldn't surprise me if these were all new copies of DQ4 with their cases thrown out to save space. After all, DQ4 was overprinted, sold poorly, and was clearanced out at a lot of places (the opposite of DQ5 which was underprinted due to sales of DQ4), so this could just be overstock being cleared out of the GS warehouse.