The car was sold with that option to the original owner. It was then sold back to Tesla at some point, and they (in theory) removed that option, though it seems like they failed to perform the update on the car to make that go through.
The Monroney sticker shows that the car had that option when new. It doesn't apply to resale, ever - there is no Monroney sticker for used cars. Nothing says it has to have that option forever - Tesla can remove it if they want, when they own the car, just like they could take out the back seats, or the radio, or put in a bigger battery, or lock it into permanent valet mode.
I am a little concerned that they issued the update after the car left their possession, so it really hinges on what they told the buyer. If they incorrectly represented to the buyer that the car had that option, through some part of the sales contract, then they definitely need to honor that. But nobody has provided any evidence of that. If they were simply silent on the issue, then it's more gray. The analogy I've given elsewhere is if a car was equipped with a lifetime Sirius satellite subscription that is supposed to expire on transfer, and then Sirius cancels it after the sale, then that seems fair.
You are correct that the Monroney only applies to new car sales, so it's not part of this sale other than serving as a piece of information about the original build.
But, a buyer who saw the sticker would reasonably think "oh, this car came with FSD," [physically uses FSD to confirm], "Yup, has FSD! Cool, it's worth $4000 more to me now." Whether or not the sales contract listed FSD is irrelevant if the car left Tesla with the option installed.
The Monroney sticker shows that the car had that option when new. It doesn't apply to resale, ever - there is no Monroney sticker for used cars. Nothing says it has to have that option forever - Tesla can remove it if they want, when they own the car, just like they could take out the back seats, or the radio, or put in a bigger battery, or lock it into permanent valet mode.
I am a little concerned that they issued the update after the car left their possession, so it really hinges on what they told the buyer. If they incorrectly represented to the buyer that the car had that option, through some part of the sales contract, then they definitely need to honor that. But nobody has provided any evidence of that. If they were simply silent on the issue, then it's more gray. The analogy I've given elsewhere is if a car was equipped with a lifetime Sirius satellite subscription that is supposed to expire on transfer, and then Sirius cancels it after the sale, then that seems fair.