Part of the confusion is Bluetooth pairing versus the "app" on the screen. As I understand it, the "My Shop" is/was intended by GM to be another App Store/Google Play competitor with a suite of apps that would use the onboard wifi, rather than pairing with/streaming from your phone. Currently there are 3 apps in the store. Dismal failure is being kind describing the effort, so there are some vehicles that have the My Shop Pandora "App" icon, and others that do not.
GM has not handled the integration of existing tech particularly well, since each has their own subscription length, a separate login for each and varying trial periods (Onstar, Sirius, Onboard WiFi, MyShop)
vi et armis invictus maneo..