It defaults to X, because it works very poorly with Wayland. Until very recently, it was impossible to run Gnome with Wayland at all (even though it theoretically supported Eglstreams), as there were many kernel errors generated by gnome-shell, etc. Now it sort of works, however, lags and freezes make it completely unusable in most cases. I am testing it every Fedora release. It _is_ possible to use Gnome with Wayland, I managed to get it working with Arch Linux once. However, it took me 4 days, manual patches (literally editing the WM code myself to fix some issues as suggested by the community) to get the configuration right, and the next rolling Arch update broke it beyond repair.

Again, I am not against Wayland. Wayland API is beautiful and I want it adapted more and sooner. It is just sad that me and many other users are not getting it. Developers blame Nvidia, because they do not open source their driver (which is a valid concern), however, there are many other binary blob drivers in mainstream Linux kernel, and everybody except hardcore open source apologists are OK with that. Why Nvidia is different, I don't understand.