I am on topic. I'm saying you can manipulate H2H however you want to make a point. Yes, Djokovic would lead by more if clay was less prevalent in the H2H. He wouldn't lead at all if Nadal hadn't played in 2011. If you remove every other match, Djokovic would lead by even more.
It's a good thing to note that so many of the matches are on clay, but remember that they could have had even more matches back in 2006/07 when Nadal was going 1-1 with Djokovic on grass and hard, then the argument would be "baby Djokovic skew" not surface skew.