I think I get the idea of Fedora Atomic (Silverblue, Kionite, etc.), but I do not get what uBlue is about.

Are those just another “ooh it’s distro X but with preinstalled Y” or are those some soft of overlays on top of Fedora? Can’t they just be some install scripts? Why not just base Fedora Silverblue? Maybe I don’t get the idea, because people seem hyped.