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.
Because “rootkit” sounds more ominous and scary than “kernel level anticheat” and the communities complaining about such things aren’t known to keep hyperbole to a minimum. Gotta push that FUD.
This article for instance, using language that insinuates a huge gap in performance between the Linux distros and windows, when it’s a 6% difference between the best and the worst, on one set of hardware.