I can't speak for car software as our stuff is completely unrelated to cars, but I work at a company whose software BMW is a client of and we do a lot of custom

I can't speak for car software as our stuff is completely unrelated to cars, but I work at a company whose software BMW is a client of and we do a lot of customization for them. I can very confidently say that of our clients (most of which are banks and some of the largest pharmas in the world) BMW has the strictest software quality and testing requirements by a fairly wide margin. No idea how that reflects on software they develop internally or for their cars but to me they care a lot about the software they have.