Because it is the replacement for Xorg and X11 as a whole. This is like expecting all Unix applications to work on Linux. No, some things need to be ported or rewritten. I don’t want to force adoption of Wayland. Heck, I’m on Xorg because Qtile’s Wayland session is missing a thing or two I need (they’re in development but not there yet). I’m just tired of people pretending this article is accurate and up to date so I wanted to set some things clear. Granted, I didn’t do it that well, but I tried.
Also, whoever calls Wayland X12 is lying to themselves and everyone else. The only way in which such naming would make sense is if you consider the fact that the X11 maintainers (pretty much all of them RedHat employees) were sick and tired of maintaining it, so they started Wayland to replace X11 (NOT as a drop in replacement, mind you). So the only way such naming wpuld make sense is if you consoder the fact that Wayland developers and maintainers were the same people that were maintaining Xorg until they just gave up.