All Teslas are built with FSD hardware included. If you pay the extra $7k or whatever it is, they just enable it for you in software. In here, they are just arguing that it was enabled by mistake and the customer never paid for it in the first place.
That's like how the BMW E46 comes with cruise control. All of the circuits to enable cruise control are in the cars from factory (except maybe not for the earliest model years). However, if you chose not to get a multifunction steering wheel, you can't activate it.
What if a customer ordered a car without the multifunction steering wheel and BMW accidentally built it with it. Couple of years forwards and someone notices that for some reason, the order sheet and the build sheet do not match. The owner takes their car to be serviced and the BMW technician switches the multifunction steering wheel panel with the blank steering wheel panel.
How can BMW at that point explain that the customer never paid for cruise control and therefore they never had it? The manufacturer shouldn't punish the consumer for their mistakes.
Which honestly doesn't sound relevant to the purchaser. My understanding is that the Monroney sticker stipulates exactly what features are included in the vehicle, as provided by the manufacturer. By purchasing the vehicle, the customer has paid for exactly those features.
This is like them saying "Oh, we forgot to charge your dealer you for the premium interior and lighting" (which is listed on the same sheet as a $5000 option) - your response would quite rightly be "Tough, I bought it from the dealer at the agreed price based on the features listed, it's mine now"
Absolutely, and as others have already pointed out, it's on the dealer to put this right. Either refund the customer, pay for the upgrade, or take the car back.