I will try my best to expain so please have a bit of patience - I am 87!
I have a Honda 2022 CRV which is not wireless so I purchased Wireless CarPlay Adapter Box 2022 Newest 5G Chip, for iPhone Fastest Speed Apple Car Play Dongle for All Factory Wired CarPlay Cars, Auto Connect No Delay Online Update, USB/Type C 2Cables, U2-Pr.
I installed that in my car - then I have my iphone XS.
The wireless adapter obviously does provide a wi-fi connection (or so it says!
After successfully using Apple Car Play and leaving the car, I have noticed that my iphone is playing the music that I was listening to in the car AND when I check setting on my phone, it is NOT using my everyday wi-fi connection but it is using the wi-fi connection from the adapter.
The only way I can get this to stop is to re-start my phone which is rather annoying.
But i have made an interesting discovery just now - when I go into Bluetooth on my phone, it has a device listed as smartBox-1E57 which is the adapter....so this is getting more interesting now. So perhaps it is the Bluetooth!