To be fair, GSP didn't try to tool either one at wrestling. He wanted to stand with them. The fact that he was able to stop THEIR wrestling, which is their primary weapon which was something they've used against several other high level fighters means GSP DID control the wrestling.
Fitch is an amazing wrestler. Just because he got taken down by BJ doesn't change that. That was a shock factor, not a weakness. Ellenberger and Hendricks will have nothing for GSP in the wrestling department. Nor will anyone at 170 right now.
I am sure he tried and failed to take Kos down many times in that fight. They don't need to out wrestle GSP they need to stop over half of his shots and commit to their strikes to have a decent chance of winning.