I think I'd adjust the wording here, as the lack of tagging isn't 'improper', it's intended.

We don't want to untag from updates-testing when moving to stable because updates-testing runs happen at a different time from branched compose. So, if we just untagged as normal in bodhi, updates would disappear entirely for a while, then re-appear in the base repo later. Ideally we would just untag them after they appear in stable.

Anyhow, I'd say "During the period where updates-testing is enabled, but before GA, updates-testing updates are not untagged from there due to sync issues. Make sure and clean those up so they no longer are tagged in updates-testing if they are in the base tag" or something.