But surely, BMW also simply knows when they sold that specific car thanks to their own records, no?
Like, imagine you were selling cameras, you sold someone a camera and then they come in to your store 5 years later with the same device - is it ok for you to ask "hey, this device has an expired warranty, would you like to extend it?" - you know this because as a seller, you have to keep a record of every device sold. You don't even need to know the owner or any personal information about them - you just know that the camera in front of you has an expired warranty.
>> And the fact that you (the driver) have an expired warranty is private data.
Well I think that's where the problem lies. It's not the driver who has an expired warranty - it's the car that does, and there's nothing you can do, EU or not, to prevent BMW from simply knowing that a car they sold at point X only had a warranty for 3 years. They don't need to know anything about the owner at all.