@mrunge messaging9s-qpid-proton-38-testing doesn't follow the sig-project-release schema so do you mean messaging9s-qpid-proton instead ? (removing 38 which is only in one tag you mention.
Once you'll have confirmed, I can quickly create the tags

Ah sorry, too much copy/paste here. These should be indeed
messaging9s-qpid-proton-candidate
messaging9s-qpid-proton-el9s-build
messaging9s-qpid-proton-testing
messaging9s-qpid-proton-release

(as you assumed).

Done :

* Checking distribution el9s configuration...
 -> Checking messaging config...
Using default options for messaging/qpid
Creating tag  : messaging9s-qpid-proton-candidate
Creating tag  : messaging9s-qpid-proton-testing
Creating tag  : messaging9s-qpid-proton-release
 -> creating messaging9s-qpid-proton-el9s
Added external repo centos9s-baseos to tag messaging9s-qpid-proton-el9s-build (priority 5)
Added external repo centos9s-appstream to tag messaging9s-qpid-proton-el9s-build (priority 10)
Added external repo centos9s-crb to tag messaging9s-qpid-proton-el9s-build (priority 15)

Worth knowing that if you need another external repo, just ask, like centos9s-buildroot, which contains some -devel pkgs not (yet) pushed to CRB repo. Closing for now