That's a clear exception. Even CS:GO from Valve runs slower than the Windows version. All other recent benchmarks keep showing Windows ahead in FPS for the same games running on Linux. And hey, I'm a Linux gamer (almost exclusively these days), and for me this is not a problem, but it's just a fact.
And who cares about benchmarks for games on DirectX 9? Especially since the OpenGL port was made nearly 7 years after the DirectX version was released, and it's possible Valve could have made all sorts of optimizations based on advances in the meantime (either in their understanding of rendering or being able to take advantage of features that are in the newest versions of OpenGL but weren't around in a DirectX 9).
