Warping of slipcased books

So, while I was browsing through the Folio Society Facebook group, I came by a post of someone talking about a curious warping of the slipcased editions versus the hardbacks with dust jackets, in humid climates. I believe the gentleman was from Florida. I was wondering if David had a comment? Is there something in the material? I'm sorry I can't link the Facebook post as I am on a computer and not my phone.