I don't get it either. But not because "software structure X11 is better than Y" reasons. X11 and Wayland are far too complex for that reasoning to work well. For example, X11 round trip latencies are a PITA over a high latency WAN, but nonetheless NoMachine worked around that structural problem without changing X11.
I don't get it because when I ran Wayland instead of X11, one thing that immediately stood out was how much faster Wayland was. As in it was less than 1/2 the time go from login screen to full set up desktop on Debian 11 using Gnome / GDM3. I showed it to friends and they switched to Wayland based on that one speed difference demo. It really was that dramatic.
When an article deviates that much from my personal experience I start questioning all it's claims. It doesn't help that the article is a long list of assertions without any data. Nor does he explain how to reproduce what he's asserting.
It sounds harsh, but it reads like an opinion piece to me. I don't know how else you could interpret: "Panel icon drag & drop:: Wayland - Quirky, X11 - Normal" as anything but a statement on personal preference.
Wayland not only has forced vertical sync it also requires every application to be double buffered. This can be detrimental for some performance metrics. That is why Wayland has worse performance despite being "simpler".