“Stable” doesn’t necessarily refer to “reliable,” depending on the context. Stable is often used in reference to how often a distro releases new versions of the applications. Using Audacity as an example, in the current release of the distro, they’ll release security & bug fixes for version 2, but if you want version 3, you’ll have to wait until the next distro release.
Upgrades to a new version of an application can introduce new ways of using the app (i.e. icons in different places, how user-created files are written to disk, etc.), which is disruptive to enterprise op’s, which is why Debian & RHEL take this approach.
Hopefully that helps clarify things.
I really like emerge/portage, even w/out the “candy” feature enabled. Great color highlighting, and verbose messages about any config change(s) needed.