His Bh was always great but just got more consistent.
His backhand has never been great before. Not only was it inconsistent, he could NOT hit the CC topspin deep to his opponent's BH (or FH if you are a lefty) at all really, and he could barely hit the BH DTL.
Even if you go back to 2004, he never pushed ANYONE around with his BH. He would get hot with it once in a while, but he wouldn't push people around with it. Now he is.