Its does not appear to be a veneer. It looks more like they cut that section incorrectly when it was being milled or there was a defect in the wood already.
Easiest thing to do would be to fill that area with a good epoxy wood filler and then sand it down. That will bond that area and deter further lift and the stain/sealer will take to it like wood.
Easiest thing to do would be to fill that area with a good epoxy wood filler and then sand it down. That will bond that area and deter further lift and the stain/sealer will take to it like wood.