It looks like the goal is to keep you from having to switch between CarPlay and your car manufacturer's interface.
Personally, I see this as very welcome, but with caveats. It's welcome in that Apple is much better at user interface design than most car manufacturers. It can be jarring to have to switch out of CarPlay to use a car function, and this would happen more often now that cars are (unfortunately) moving toward screen-based functions rather than switches and knobs.
On the other hand, this is only useful if Apple is open enough to let manufacturers greatly customize the CarPlay experience. Fortunately, there is some evidence that this will be Apple's approach, but the proof will be in the details.