I can comment about plays since I've retired from the field and gone to the dark side with "media". It's not critical, just for helping with discussion and understanding.
I was surprised more about the replay announcement than the ruling the play stands as called. The replay shows the runner losing control of the ball prior to the knee touching. Now the problem comes in that we lose sight of the football and only see the defender tugging to pull it away. We can't see the ball or either players hands as both go to the ground. All of a sudden the defender is up with the football. TV didn't have any other angles to show us or possibly the replay booth. My gut says Team B "probably" got the ball but you can't prove it with any indisputable video evidence. Whether the Team A player re-controlled it on the ground or the Team B player had it.. replay could not rule on a recovery that's not clear... Rule 12-3-3-d: "Loose ball ruled dead, or live ball ruled dead in possession of a ball carrier when the clear recovery of a loose ball occurs in the immediate continuing action." Possibly replay got a view we didn't see and had reason to rule the runner down. We were so focused in the booth on the original feed that there probably wasn't time to get other feeds from the truck, possibly the replay booth did.
The interesting part of the process was the FST that allowed time for the play to be shut down or challenged. I love replay to death but like the officials on the field and in the booth, it's not perfect. It's a machine run by humans. Heck, I may be wrong about what happened... did that a few times on the field.
