Note that it's not necessarily an "Arch distribution" in the sense you might expect:

> KDE Linux is an immutable distribution that uses Arch Linux packages as its base, but Graham notes that it is "definitely not an 'Arch-based distro!'" Pacman is not included, and Arch is used only for the base operating system. Everything else, he said, is either compiled from source using KDE Builder or installed using Flatpak.

This sounds fairly close to SteamOS in terms of structure. (Which seems to work well for its own use case, so I can see the logic.)