There's no such thing as "Wayland input latency". It's just a word salad, akin to "HTTP animation smoothness". The post is measuring Xorg vs. KWin (and also XWayland), other implementations of either X11 or Wayland will have different characteristics.
I wonder where the XWayland's added latency comes from though, it seems suspiciously high to just be easily hand-waved as overhead.
I wonder where the XWayland's added latency comes from though, it seems suspiciously high to just be easily hand-waved as overhead.