The descriptions in the article are very handwavy (especially on the X side) and they blame X for things it doesn't do yet while at the same praises Wayland for

The descriptions in the article are very handwavy (especially on the X side) and they blame X for things it doesn't do yet while at the same praises Wayland for things... it doesn't do yet either (HDR). However the measurements at least are good (interestingly i was actually planning to do the exact same thing at some point using pretty much the same approach) and basically show what most people expect: X without a compositor (or with the compositor being disabled for fullscreen gaming, though note that not everyone may want to play games in fullscreen - e.g. i often play games in a window myself) and vsync disabled provides the best responsiveness. Also one thing that should be made very clear is that these are about KWin/X11 and KWin/Wayland, not X11 and Wayland in general. For example last time i checked XFWM allows disabling vsync in the compositor, which would certainly affect the results here. Also it isn't made clear (and actually i don't know myself) if KWin disabled the compositor for fullscreen Wayland applications or not: i'd guess it doesn't because under X in my laptop where i use KDE i had to explicitly disable it even for fullscreen games (there is a shortcut key for that), so i'd expect the same behavior in Wayland too.