Yeah, I'm a little suspicious about that claim.
replyBluetooth tethering is a thing, actually predates wifi tethering. Though it's not enabled unless you enable Personal Hotspot in your phone settings (and Android requires it to be enabled separately).
CarPlay complicates things, as it only uses bluetooth to pair, then it switches to using a wifi network (as bluetooth doesn't have anywhere near enough bandwidth). Maybe Apple automatically shares internet over that carplay connection?
I have no doubt that the car will use the internet connection if one is exposed, I just doubt it will be exposed automatically.
My iPhone automatically shares the internet without enabling hotspot with my Toyota via Bluetooth. It happens automatically. I just start the car, and it happens. And CarPlay is not involved, since there is no such thing in my car.
replyOne thing I notice is that it doesn't appear to upload contacts from your phone in usb mode. I haven't confirmed this.
replyBluetooth tethering is a thing, and I believe is enabled by default on Android, maybe it's using that?
replyFor me on Android 16, the setting is in Network & internet > Hotspot & tethering > Bluetooth tethering