In Fedora, there is a base OS version with a sort of configuration, specif directory structure, major architectural versions of software (like Gnome or KDE), sometimes cryptographic policy, or other system backends such as logging or DNS resolution.
Fedora used its release cycle to migrate to systemd-resolved, to pick an example, because this change introduced structural changes to the way the system operated. In the release in question, system services leverage the D-Bus API to get DNS lookups, systemd binds to the local port. By segregating this behavior by release, it makes the dependency tree much simpler to manage at the cost of possibly needing to backport patches, but Distributions are doing much more than shipping mostly upstream packages like Arch is.
I always thought arch would be well suited to this sort of thing. Arch Build System is very good, and since packages are very close to upstream, it would be very easy to make your own ABS repo as it stands. It is very similar to the ports tree, arch linux has very little flavor in many respects.