Merely "Not playing the ball" does not constitute P.I (that used to be a penalty back in the day). Making contact with the receiver while not playing the ball does make it P.I., but its a judgement call as to how much contact there needs to be. We've all seen the play and people are on both sides of the call which means it was very close and could've been called either way. It wouldnt have been all that controversial if the refs hadnt called it, announced it, moved the ball, then moved the ball back without even announcing they were uncalling the penalty.
Ive seen plenty of fumbles and other judgement calls that the announcers thought went one way, I thought went the other way, the ref went one way and Mike Carey or Mike Perreira insisted they were wrong. Happens all the time.