I don’t believe it. Apple R&D will have lots of research toys they play with (folding phone for years reportedly) and I’m sure there’s a giant iPad in there. But these giant “tablets” are not really tablets, they’re ultra thin monitors with a touch screen. Basically take the chin of an M1 iMac and add touch.
Dave2D had a great review of Samsung’s giant tablet. He loves it but was clear this isn’t for people looking for a handheld tablet. But that is what a tablet is.