You can't just test one wayland compositor and talk about the performance of all wayland compositors. They're vastly different, especially when it comes to the extensions to wayland needed to handle input devices (ref: https://wayland.app/protocols/). It's not like how xorg is the standard strong reference implementation for X11 everywhere that works the same everywhere.

What's probably happening is that other wayland compositors are slower than KDE Plasma wayland which he tested. And people report that experience. Some other wayland compositors might even be faster than plasma. But what is for sure is that every wayland is very different from every other wayland.

You will also get different results by gpu, compiler, kernel, architecture, and then of course compositor. Even a slightly different version of some lib might throw off the results.

In any case the methodology in the post is sound and should be used for benchmarking in the future.

And FWIW, KDE probably make the most effort with their compositor. They have historically been well ahead of the curve for things that might affect this (e.g. VRR).