I once hear Simon say it is difficult for the judges to hear what the contestants say during the feedback portion. I've wondered if they have problems hearing what is said, is the same true for what is sung?
I wonder if AI is a bit like ice skating in that the judges watch the practices and form an opinion then. Sometimes you hear a comment like "you nailed it in practice, but this was a train-wreck." That could also explain why sometimes a contestant gets ripped for a performance that I thought was pretty good, or like Jason, gets praised for something that was really bad.