Recent testing revealed that Arch Linux, Pop!_OS, and even Nobara Linux, which is maintained by a single developer, all outstripped Windows for the performance crown on Windows-native games. The testing was run at the high-end of quality settings, and Valve's Proton was used to run Windows games on Linux.
They probably didn’t label their axes properly. FPS is a clearly defined metric, and there, more is better. This indicates that the conclusion (Linux is faster) holds. Since frame times have an entry with value “100” and all other values are lower, I assume that’s in percent, i.e. Arch Linux is the fastest and picked as comparison point, and the others are shown with relative performance to Arch.
It says “Prozent” in the bottom left of the screenshot. You are correct. They use percent to compare them. So more is actually better here.