The ball pitched on the line of middle stump and was going to hit the off-stump. Mark Benson had the doubt of whether the height was the problem, I assume, and even with the review, his decision should have been reversed.
Yeah height was the problem, it was hard to tell so he probably just let the on field umpire give the call on his first impression. But to me, I would have probably given that out. Kumble gets like 20 legit LBW appeals turned down per game so I think the review system will come in handy for him.