Concerning high end audio names in new cars

20 years ago I bought a new car with Bose, it was incredible. Better than anything I had heard before in any car. 

A maker is totally at the mercy of the varying, hugely challenging acoustics/materials in the myriad of car models

or they get a car, fully completed and they can tweak their system to sound the best

There is an Italian company by the name of Audison that offers "Sound Packs" for quite a few specific manufacturers and models. I have an all Audison sound pack in my '17 Golf GTI which includes a sub in the spare wheel well that does not require removal of the spare. I had sound deadening installed at the same time. It is good. Nowhere close to a good home system though. 

I have a "Fender tuned" system AKA Panasonic in my 2017 VW GLI and I think it sounds just fine. I wasn't expecting much after all I am listening in a car.

I have never gone into car audio with the expectation it’ll be anywhere near home audio quality, for reasons many have stated. Especially as many of our home systems cost as much if not more than many cars entirely. If a car’s sound system is enjoyable for what it is, that’s what counts. I’ve felt lot of it falls on sources and EQ which some manufacturers provide more adjustment and flexibility than others.

My fiance’s Harmon Kardon in the X5 sounds much better than the Bose in my A6. My old A6 had Bose and in some ways, sounded better than my significantly newer one. Are either ’audiophile’ quality? Nope, but in 90% of my experience optional systems sound better than base systems. As should be expected. Is it worth the price? That’s up to the individual.