The recommendation comes from the iPhone app.
Apple Watch
Your coach on your wrist.
Choose the session in the iPhone app, send it to Apple Watch and leave your phone at home for the run.
Sync
Plan on iPhone, run on Watch.
The Watch app must be active and the screen should stay on.
As soon as the iPhone is nearby again, the run is transferred.
More help with Watch, sync and individual runs is available in the FAQs.
