Once you trade it in, Tesla can do what ever they want. If you sell it privately then it should stick, just as FSD would.
Asking them to transfer it, ha ha ha, nice try. We are talking Tesla.
Keep in mind, any "SOFTWARE" option it worthless to Tesla on trade. And they can sell the software options again.
Now if it was traded or sold to a Non Tesla dealer. It could end up like free supercharging. I'm not sure what they do with FSD in this case, I think it sticks. Boost would probably fall under the same treatment.
Oh, Free Supercharging is only original owner and that I believe is called out. So even if private, that goes bye bye.