If the ball carrier is falling backward to the ground and gets licked just before hitting ground, do you flag the defender? If the ball carrier is running sideways to the sideline and is just about to obviously step OOB and gets licked, a flag? If no on both counts, why would you have a flag in this case? The rules makers want the ball to stay live in this case, and they get to decide, not us.
Good whistle control from the covering officials.