Quite a lot of games run the same or better on Linux, converting Windows system calls to Linux ones isn't much of a performance hit, and often the lean-ness of Linux overcomes it. It's not like emulation where it's always going to be worse.

The issue is more to do with some anti-cheat implementations (namely ones that rely on installing a kernel-level windows rootkit), and GPU makers not contributing many "game ready" drivers, I.e. patching game issues in-driver.

That second one is why Linux framerates are on average higher, but the .1% lows tend to be lower.