Okay, game speed is faster than practice speed. Some guys just take in information better when it is for real. Casey makes better decisions and delivers the right kinds of throws at the right time. He doesn't get rid of the ball quickly, he DELIVERS the ball quickly.
There is a difference between getting reps with the 1s and the the 3s. Practice time isn't unlimited. No way he was getting as many reps and getting the same quality of reps.
Was the line playing better? Of course. But it since Casey makes better decisions quickly it's not like we have an expectation to block infinitely now.