I mean serious warped. The center the bulge is about 1/4" high (low). The MDF is fine. I suspect the nice people at IKEA oiled the top surface and not the bottom (which is the side that swelled).
I've decided to go with a third layer of MDF and laminate 1/8" hardboard all around to finish it.
Maybe the hardwood will flatten and can be used for a table. Or a bowl.