To be clear; the Superchargers are effectively dumb devices (12 Model S Gen-2 Chargers in a box). The BMS in the car 100% controls them. So when Tesla disables supercharging on an unsupported vehicle, which is not only salvage, but also grey market cars (when cars are moved out of their home market), they actually reach into your car over the internet connection and change the configuration option to disable it. They are modifying YOUR property without YOUR permission. It would be different if they just weren't delivering power by blocking it on the supercharger side, but no, they alter your car.
If their argument is safety, which of course is valid; then they should offer a free or low-cost high-voltage safety inspection to re-enable it. Supercharging is a paid feature, not unlike upgraded wheels. Them reaching into your car to turn it off, is not unlike Tesla techs showing up in a van in the middle of the night to steal back your upgraded wheels. And the safety argument, especially on a gen2 or newer car is really a tough one, as the car's' diagnostics are so good that any HV (high Voltage) issues would cause a fault alert which would shut down or throttle supercharging to prevent bad things from happening. On Gen1, those cars had non-instrumented HV junction boxes, so it's possible that damage or improper repair in this area could cause a fire during supercharging. (Gen 1 cars are Model S VINs around 30,000 or lower, so not that many cars)
I have worked on over 600 customer cars now and re-enabled supercharging on all of them that have been disabled. I've never had one of them have anything dangerous happen as a result. I work with the owners to assess the condition of the HV system to make sure it's safe to do so.
I have had a handful of customers go though the expensive inspection process only to be told; "Sorry, no supercharging for you", even though the car passed. Now that Tesla has finally agreed to sell parts to unsupported VINs, there is no point paying them for an expensive inspection, as you really don't gain much. (Only that Tesla will agree to preform repairs on your HV system!)
In September Tesla issued this: (Note the last sentence on the first page which says they WILL sell parts, and the last sentence on the second page, which is no Supercharging for you, EVER!)