The blog post says they're just deprecating X11 APIs at this point; GTK5 will remove them.
I'm still very worried about this. Wayland still has many rough edges and I think forcing a move to X11 is premature. One of the main benefits of the Linux ecosystem has always been that it strived to run on hardware far longer than commercial vendors, who have gotten even worse at forcing obsolescence of hardware for purely revenue-focused reasons (looking at you, Microsoft -- Win11 refusing to work on chipsets it is perfectly capable of running on...)