Not sure how "hosted on the same domain" transforms into "developed by the same group". I've seen many independent small github projects that were transferred to freedesktop, how they banned Hyprland, etc. They also host a variety of topics (and even more in mailing lists, from systemd to libreoffice), not just desktop-related, managed by different teams.
- https://gitlab.freedesktop.org/xorg/xserver
- https://gitlab.freedesktop.org/wayland/wayland
It's not just that developers migrated to a new project. Wayland is essentially the successor to X and is developed by the same group.
(That doesn't mean there aren't still lots of bugs and sharp corners.)