Some Automotive Head Units experience this when using CP2A/CarlinKit 4.0.
The screen of wireless CarPlay, full screen.
Wireless Android Auto screen, not full screen.
Solution:
Use your Android phone, connect to wireless Android Auto, use your mobile browser, enter 192.168.50.2, try to change the resolution to 1280*720 or 800*400, and then observe whether the screen is full screen.