I had that exact same thought when I watched BTTF 3 tonight. You totally read my mind. The name on the headstone changed and then vanished. Hmmmm
Yes, that’s right, the name changed from Doc’s name to Clint Eastwood (the alias Marty was using) then events changed again and the headstone dissapeared entirely.
Aaaaannnd now I’m getting visions of Neal’s headstone vanishing and the rose that Henry laid on top dramatically falling to the ground in slow motion.