Someone smarter than me can probably explain this way better…
As far as Wayland goes, If I remember correctly, it’s mainly just a protocol, and Gnome/KDE do all the actual work of making stuff happen, so both need to support it to have it work correctly. Like if Wayland was a language like French, Gnome and KDE need to know the French words for something before they can have conversations about it, and Gnome hasn’t been as studious with it’s dictionary in regards to VRR. X11 just has an ancient code-base, and adding support for anything involves a lot of effort to make sure something else isn’t broken by the addition.
Gnome hasn’t officially merged support for VRR yet, but there is a merge request to add support, and a patched version built on that code available if you want to try it (mutter-vrr, gnome-control-center-vrr) at least on Arch Linux’s AUR.
“No thanks, I’ve already played Assassins Creed: Black Flag like 10 years ago”