First of all the referee is out of position to make the call. He should have stationed himself at the end of the table where the cue was traveling toward him. Many referees think they should not be in the line of sight of the player when he's shooting. Wrong! A good referee gets into the best position possible to see the shot develop, particularly on a shot like this. Then he needs to stand still! That way he's in a better position to see what happens before and after contact. Where he was standing, behind Shane, he has no chance to make the correct call here.
Interestingly enough, we can actually see the shot better on this video than he could, because we are in the line of sight of the cue ball path. This is the hard part, making the call. It all happens very fast and you need to watch closely the path of the cue ball. Something definitely happens to deviate it's course, and it isn't English taking after the cue ball is a diamond off the rail. As the ref, if you see the shot and hear a sound, it's a foul. After watching it several times, I believe the cue ball came into contact with his tip after the shot. That caused the quick deviation in the path of the cue ball.
You'd have to slo-mo this to really see the foul more clearly. Notice where his tip is when the cue ball swerves abruptly. Shane probably felt the contact as well. One more thing, if you watch closely, Shane hits center ball on the cue ball, so there wouldn't be any English coming off the rail. The correct way to shoot this shot is center ball with no English. It's just too hard a shot to add English to the equation. He fouled!