I can see where some type of compensation from the third party seller would certainly be warranted if the car was advertised to have free supercharging or even Full Self Driving or AP and Tesla removed any one of those features. The free supercharging is probably the hardest to determine a fair value for since Tesla only sold it on the early 40's and 60's for $2,000 extra. So that's the only gauge on it's "value", but that was 8-9 years ago. FSD is easier to determine market value and is a feature that's typically listed on the window sticker, unless the owner purchased it after the fact. As with any type of case, they likely negotiated an amount that was agreed upon by both sides. The buyer certainly would have had justification for a lawsuit against the third party dealer for selling something that doesn't exist. Oops wait, maybe not, Tesla's been doing that for years! LOL. (Full Self Driving, New Roadster). Glad it got resolved for the OP in apparently, a satisfactory manner.
My recommendation, after having purchased and sold several Tesla's, if ever buying a used car from a private party person, ask the seller to set up a separate account for their Tesla that they won't need anymore, Then, DON"T TELL TESLA YOU BOUGHT IT!! Things with the car will stay the same. Simply change the e-mail and password on the EXISTING account and take it over without filling a transfer of ownership with Tesla. Naturally, still have to register the car in your state, but that's separate from telling Tesla you bought a used car. Tougher to do if you purchase it from a third party dealer. Unless the dealer is willing to contact the prior owner to get you access to the account the car is under in the same manner. Something a smaller deal "might" consider, but not probable and certainly unlikely from a larger dealership.