Does `await` really make sense in `db.collection('rooms').doc();` ?

https://github.com/webrtc/FirebaseRTC/blob/b1d98aa103eb63b6874d52b2023b25fba81cbd50/public/app.js#L33

According to the [docs](https://firebase.google.com/docs/reference/js/firebase.firestore.CollectionReference#doc), the `doc()` method doesn't return a promise. So why the `await` in this line?