Apps cannot open the settings application to a specific screen. The reason that apps like MapMyFitness open preferences is because they ask for permission to use Bluetooth Low Energy. Asking for permission is managed by CBCentralManager on first usage.
This is also the class that knows if Bluetooth is turned on or off. It will show an alert automatically with an option to go into settings to turn bluetooth on.
A similar popup will be shown when using location services.
These popups are shown automatically by the system framework. The message can be customized using the purpose
property for location services, that is not possible in case of Bluetooth.
No private API was used for this, so there's no reason for the app to be rejected.