Only those first 4 are within the ublue project. The others are just part of Fedora, different variations of Fedora immutable distro.
A ublue can be rebased to the Fedora images. So you could go from having Aurora to having Kinoite for example.
That repository of images you linked to you can get from the project pages. Like the Bazzite page will say “are you on handheld?”, “do you need game mode?” “Do you have nvidia?” And then link you to the appropriate version from that repository.
There might be deprecated versions in there, for example I know they don’t maintain the Surface kernel version anymore.
Ublue will happily include media codecs, nvidia drivers, ootb hardware acceleration… the things you would likely do with a Fedora image - but Fedora can’t or won’t include by default due to strict guidelines on their project or legal concerns.
Side other niceties like ublue includes distrobox, which is commonly used in other immutable distros, but Fedora don’t include it.
It’s basically overcoming Fedora’s limitations as a starting point. And It’s not downstream, it’s more alongside Fedora, you’re essentially running Fedora with ublue’s optimisations plugged in. When Fedora’s updates come through, you’ve got them.
And here’s the mission statement https://universal-blue.org/mission.html