Tag warnings pop up (best I can tell) the first time focus leaves the "tags" field. I suspect many users post following the natural top-bottom order suggested by the ask page: title, text, tags, click "Post Your Question." (Perhaps a UX expert on SE staff can tell us how common that is?) Which gives us the following experience: Tag warning only shown for a second when I post directly after adding tags.
Is it possible to change when the tag-warning displays to improve the chances that people who need to see them actually do while there's time to re-think whatever the warning's pointing at?