I seriously agree with your stance. The only thing has my head scratching is how to solve the complete top to bottom integration that gives Apple an edge... the M1 macs have proven to be something that only Apple, at least at this time, can do (i.e, Intel trying to play catch up with the bigLITTLE cores mindset will be met with a lot of friction because for example windows x86 isn’t made to take advantage of that power management yet).
Maybe that’s why they could be aiming persistently to at least a partnership. But MAYBE this is one thing that doesn’t really need it, however the slow rolling in regards to CarPlay sets a precedent in my mind.
They could build the entire "brain" of the car, including the entertainment system, all the cameras , all the radar sensors, all the lidar sensors, all the parking sensors, ... including the WiFi Access point, including the 5G modems, the Qi/magsafe charger, ... and do things like updates to the car's software centrally from Apple.
That way they can still work with the car maker to let them pick where they want what buttons, where they want what screens (HUD, instrument, entertainment in the rear, ...) yet give all cars up to date maps, let them play apple music, get your games in the rear, etc. While updating the car's "smart" part like Tesla does.
The car maker then still has all the other luxury the leather, the wood, the engine's power, the looks of it all so they still can differentiate even outside of what options they enable together with Apple.
I obviously can see that car makers are not eager to give up too much control, but they all are hurting badly (making cars is not that hugely profitable - not by Apple's standards), some are trying insanely big mergers (PSA/FCA e.g.) to merely survive. So offering them not to have to develop the self-driving aspects might be a big selling point. As it's a huge money drain to develop it for many, many years before you can get the first returns.
No deep pockets and you can forget developing it. As even Mercedes-Benz can't (or won't) afford doing it ... just imagine being a smaller player.
The same goes for Apple too: they're used to high margin products only. Cars that are high margin ... that's the very top of the market - it's not what people out here buy. And those are bought by people who're not easy to part from their palaces on wheels. Moreover the car itself (body/suspension/engine/etc.) has a huge cost to develop be it a battery-electric or more conventional system. Most car makers outside of the very top models can only do so by using platforms that share the same basis outside of the aesthetics in order to get enough volume to pay back the development costs. Unless anybody around Tim wants a repeat of the solid gold Apple Watch "S0" Edition (the 10K US$ one) they'd better think twice how to avoid making a car nobody but a very few will ever consider buying full price.