Yes, basically. uBlue doesn’t maintain distros, really, it just repackages Fedora Atomic with some minor changes (including non-free drivers, for instance). That way if you need the software they repackaged into the image (like Nvidia drivers), you don’t have to use overlays, and instead can use uBlue images. In fact, you can actually rebase Fedora Atomic to uBlue and vice versa with a single command. All it does is change where the base images are fetched from, and it’s a potentially easy way to switch between images without having to perform a reinstall (do note that different packages in the base may modify config files that will persist between rebases, though). I haven’t personally tried it, so I don’t know if there’s a likelihood to run into issues, but it’s an interesting option nonetheless.