The on device display is basically a dumb remote terminal. Those are easy to stay compatible forever. I can still AirPlay from my an old 1st gen iPad to a new Roku TV. I can still print from an old IPad to a new printer.
The fact that Apple and Tesla aren't good stewards of mission critical car software is, in fact, the fact it's trivial to push updates. It means they can shove out stuff with less validation and fix it in post. I would contend that easy patching nearly guarantees poorer software development correctness.
Consider the fact that no Nintendo GameCube game has to be post-launch patched, and while some flaws do exist that speedrunners can exploit, all of the games still work, decades later. Compare that to modern games, which often require a "day one patch" to fix them.
I absolutely trust a traditional car manufacturer to release better software than Apple or Google. It may not be as pretty or have as many bells and whistles, but it probably isn't going to kill me.
It could be argued that this is for slightly different reasons - because of the delay between a game being submitted to console manufacturers for testing and release, and the "crunch time"-style industry of game dev, I'd argue this is mostly to try and get the game launched sooner, because its cheaper/faster to ship a buggy game on disc and fix it on release day than to wait until the game is entirely fixed first, now that it is a viable option
(Not to disagree with your point - I completely agree)
Your car isn’t going to crash because Apple Music is flaky.