Fred, sorry, but that is nonsense. Wayland supports GTK2 - btw has nothing to do with it, nothing and I can prove that at least for for the Raspbian implementation.
GTK2 is a widgetset, (like MSEgui

) that uses a graphic window server, like X11 in some Unix distro, for rendering.
Afaik, GTK2 cannot use Wayland graphic compositor and so, thanks to XWayland project, mainly all applications using X11 can run with the XWayland-kind-of-X11-emulator installed on some Wayland distros.
So, ( I did not check ) it is highly possible that Raspbian-Wayland distro has XWayland installed.
[EDIT] Yes, htere is one Rpi OS-Wayland version but experimental :
https://www.phoronix.com/news/Raspberry-Pi-OS-Wayland