That may be true, but de facto defaults today is Proton experimental on Steam with the a recent Linux kernel. That's pretty much the same across all distros.

Sure, but each distro has a default configuration, and distros don't vary that much in terms of performance with those default configurations for playing games. If there is a consistent performance difference, it'll likely be something like 1-2%, which should be within run-to-run variance and not really impact the results.

And if anyone assumes that an average between 10 games represents the difference you'll see on average for your own games doesn't understand statistics because 10 games is not enough to be a representative sample, especially since they weren't even randomly selected to begin with. It's still an interesting result.

CPU bound... Linux is going to destroy Windows

You're being hyperbolic here.

The differences, all else being equal, should be pretty small most of the time unless there's a hardware driver issue (e.g. when Intel's new p-core vs e-core split came out, Windows had much better support).

If we're seeing a huge difference, more is going on than just a "better" scheduler or more efficient kernel or whatever. It's much more likely Windows is using DirectX and Linux is using DXVK or something. The bigger the gap, the less likely it's the kernel that's doing it.

As someone who has used Linux exclusively for ~15 years, these kinds of benchmarks are certainly exciting. However, we need to be careful to not read too much into them.