Do you have a source for that? I can't remember it, I know he said that Wimbledon was still the fastest out there, but has he said something about the USO?
No i'm pretty sure i read tis in 2011 but i can't find any link.
As you said, there are plenty for Wimbledon, though. He said that the grass is the same since 2002, even Mouratoglou, who likes Rafa a lot, laughed about that. But hey, sure, Nadal won't complain about a change which is good for his game, but still, he is selfish like every top player.