The PGC isn't mandating that you have to hunt the Saturday after Thanksgiving. Those who want to conform to tradition can still keep their tradition and start on Monday. Those who love the hunting more than "Prep Time," can start on Saturday. It's that simple.
IMO, I really don't buy the "Prep Time" excuse. I find it impossible to believe that anyone has to wait until the two days before a season opener to get bench-time with their chosen firearms; getting their gear sorted & packed; getting the food & drink situation in order; getting the camp in order; etc. Ditto that for small game hunters, archery hunters, anglers, etc. Right or wrong, that's my opinion.