They would get a hell of an earful from me if they tried to pull that BS. It is one thing if they buy the car back and resell it themselves without upgrades but it is entirely another to remove it after the fact when a person paid a price on the used car based on that feature being included. I can't imagine that'll stick, it is a PR nightmare and a lawsuit waiting to happen from every owner that ever purchased an upgrade from them.
I don't think this is applicable to my situation anyway. The dealer I purchased from took the car as a trade from a private seller, it never went back to Tesla at any point since the initial sale. The situation you are talking about sounds like Tesla meant to remove Autopilot and FSD when they sold the car at auction but didn't actually take the features away.