What makes you say that? We haven't seen him fight anyone with a great ground game that tried to take him down. Diaz didn't try the first time, and Gurgel inexplicably decided to stand with him. We haven't seen it from Noons. I think Diaz could pull guard and submit him.
Of course did Nick tried to take him down in the first fight. He knew, if he would continue on the feet he would get Knocked Out. He even succeeded ones.. but failed in most attempts.
KJ already showed amazing TDD in this fight.
I just don't believe Nicks Wrestling is better then KJ's TDD. And even if he get's him down, just take a look back and watch again how easily KJ was able to stand up again.