I happened to see this, as I tuned in for the last part of Georgia's comeback, including of course the apparent non-touchdown to take the lead, which was not overturned. ( It was very very close, either way. )
In the Louis touchdown, both defenders were to one side of him. One of them just about had the interception when the other defender reached across him and tipped it away, and into Louis' hands. You could see this in the replays.
Also note Georgia came very close to scoring yet another touchdown in the closing seconds, when they had several tries from around the 20 yard line. So, an amazing finish, all in all.
I don't know. When CBS had the split screen it was clear to me his knee was down on my 75" HD screen. I wonder if the refs had that technology available to them?