So I skimmed the actual article, not sure if the author said this, but my guess as to why Wayland has a ... worse reputation generally in the latency department, than seems to be deserved?

At least for myself, there was a significant period of time where ... XWayland was the only way to actually run whatever game, on my system, with/via Wayland.

If this kind of thing was not just myself, and was generally common... well then XWayland = Wayland -> Wayland sucks.