OK so that took a bit of Googling. Apparently GnomeOS is Linux Distro with Gnome and its dependencies all installed and configured correctly and is intended to be used as a reference platform for developers who write Gnome apps.

Why is it so hard to actually put that on the website?

It's still very new and a very small team, i would suggest reaching out and maybe asking them to add that to the website, seems you summed it up perfectly!

I thought that was Fedora’s role...

har har..

Is it based on Ubuntu?

Doesn't seem like it's based on any already-existing distribution:

https://events.gnome.org/event/1/contributions/80/attachment...

Nice!

KDE Neon is. It’s what I use when I have the rare need to use Linux on the desktop.

Basically Ubuntu LTS, but canonical and gnome don’t get to make any poor UI decisions. They even ship a stable version.