If you have experience on Linux package managers, these will not look Greek to you.
Take "yum" (the package manager for Fedora. Actually it's for a lot more distros too, but I haven't touched Linux for a long time, so...) for example. When you open the config file, you can see the main repository, the extra repository, plus a commented section for the "devel" repository. If you uncommented the devel repository section, yum will also check and update the "still cooking" RPMs for you so use at your own risk.
This allow corporate users to deploy test VMs to test the RPMs against their company's configuration, and alert the RPM maintainers if the RPM "does not cook right". So for each "stable releases" RPMs there will be lower chance of problem (at least there will be unlikely to be any problem for companies who participated the devel-release tests)
That's the whole point of the change.