This tradition has been transmitted by Ibn Shihab through a different chain of narrators to the same effect. This version adds:
He would observe witr with a single rak'ah and make a prostration as long as you would take to recite fifty verses before raising his head. When the mu'adhdhin finished his call for the dawn prayer and the dawn became clear to him.... Then the narrator transmitted the rest of the tradition to the same effect.

Some narrators added something more in their version.