Well, he does only play chamber. He is the best in the world at his role, no doubt about that. But like there are other players who are world-class in different roles too. He could be considered the front-runner for the best player in the world based on general impact of a match. So basically he is:
-Definitely the best chamber in the world,
-Possibly (at this point quite probably) the best player in the world (based on impact), but there is still a discussion to be had on this point