Like with smart TV with advertisements, the locked down cars will provide revenue after sale for the manufacturer. Thus they will mass produce and sell those cars for a cheaper price, while adding a significant markup on the non-locked down cars to be primarily sold to commercial partners at lower batches. The cheaper mass produced one will significant out compete the other ones to the point where most dealers will no longer sell those more expensive versions. Most customers won't even know the difference when they buy the car, and why should the seller go out of their way to inform the buyer when most people just care about the sticker price anyway.
Having locked down products also allow the manufacturer and dealer to form a agreement of sharing some of the post-sale revenue. The dealer can have their own shops for repair which the customer are now forced to use, naturally at a steep markup, and the manufacturer get a slice for every repair. The cheaper sticker price can then be decreased further since the dealer now have an additional revenue after sale. The customer can go to an other manufacturer approved shop, but then how many of those exists in the same city, and the manufacturer can artificial limit how many shops get approved in the same location.
The story is the same across any number of industries right now. Customer choice is not a argument for the manufacturer to not do it. If you as the customer want to opt out, the only choice after a while will be to not buy a car or buy the expensive ones for double the cost.
If you crash into a BMW, you'll still have to pay for the now-inflated cost of the repair - most likely through the mandatory liability insurance. Insurance premiums have gone through the roof, to a big part not just due to insurance company greed but because cars and repairs to them became more expensive.
