Opensuse doesn't have rpm-ostree. Their immutable offerings are just snapper/btrfs snapshots before changes to the system.
Such a setup is nowhere near as powerful. rpm-ostree can rebase itself based off of a container/oci image. It can layer images on top of eachother. Rather than just tracking when changes happened, it can also track what change happened, in a git style setup.
Oops... my bad. In my earlier comment I assumed that this would be a Fedora/Ublue based distro, rather than an Arch one. Arch doesn't have RPM ostree either (which makes me dislike it as a choice for an immutable distro).
But, it's highly likely that with the steam deck and other projects, there is already an ecosystem for immutable Arch, and a minimal base system to start is advantageous, as Possibly Linux said.