This is true across every vehicle I’ve ever been in. There are a number of reasons: 1) they both do use the car’s gps, as the phone gps within a vehicle is less reliable (due to, in part, metallic tint and being inside the vehicle) and thus they use the vehicle’s chip which is housed outside the cabin.
In addition, there are many safety regulations prohibiting you from using multiple maps, etc.
I’m not an expert on the regulatory piece, but it is true across CarPlay-enabled vehicles, to my knowledge.
You are mistaken. For wireless CarPlay, the vehicle providing the GPS is a requirement. For wired CarPlay, it is optional (and can use your phone’s GPS), but the vast majority of manufacturers implement it anyway. Apple prefers it, for the reasons mentioned above.
Same.