Thirty years in the trade and I never once thought to seal the back of a panel. Two summers ago I had a client's desk top split right down the middle, blamed the supplier for bad stock. Turned out the back was bare while I had finished the front with three coats. That Lancaster guy is onto something. I have since started using a thin coat of sanding sealer on both faces of any wide panel before I even cut the joinery. My last six jobs, not one call back. Feels kind of dumb to admit it took me this long, but I am glad it was just my process and not the wood.