Okay. So the NCAA issued some clarification on this (for the Ole Miss play at least).
Replay and non-replay games work by different rules. What I said is true of the field crew without replay. What Huck said is true of replay. And field crews with replay should let plays continue when it's not clear.
The Ole Miss call on the field was actually a backwards pass with an inadvertent whistle killing the play. The Line Judge (camera sideline) called it backwards, but the Head Linesman (far sideline) blew it dead thinking it was forward. Line Judge, who is the official with primary responsiblity for this type of call, presumably won in the discussion.
So the booth didn't change the ruling to a fumble, but they did rule that there was clear recovery.
This is still really bizarre to me. There's two players closer to the ball who stopped playing after the whistle and it isn't like a bang-bang recovery where the whistle blew right as the ball was being recovered.
Isn't the entire point of the whistle to be an absolute end to a play? If the booth can actually overturn a whistle, this is going to encourage post-whistle play and the injuries and fights that follow.