It is very simple. The bare minimum Arch install consist of the base <https://www.archlinux.org/groups/x86_64/base/> group.
The user *must* install this group. If they don't, they no longer have a minimal Arch install, so developers cannot help them. It is the *base* and everything else builds on it. It would make no sense to replace the *linux*, *filesystem* or *pacman* package with something incompatible and expect everything to keep working. Now, it would be technically possible to replace *systemd* in base with a generic "init-system" which could be provided by both *systemd* and *openrc*, but that would make things much more complicated and *much* more effort to maintain. Regards, Sebastiaan
