https://bugzilla.redhat.com/show_bug.cgi?id=834012
Both headpin and subscription-manager-gui reach out to the CDN to get a list of available release versions (5.8, 6.2, etc.). Katello, however, bases the available release versions on the subset that have repos enabled.
With that in mind, I think the BZ above is working as intended, ie. release versions shown in subscription-manager-gui have nothing to do with what katello has available.
I think there have been BZs/RFEs that systems should not be able to set a release version when registered to katello to a version where no repos (and hence no content) are available.
Someone with more knowledge of the feature and intricacies please chime in.
