We've found a bug which was introduced in 1.21 that admin now can't override policy via --force when tagging a build. There is an issue [1] and fix proposal [2] for that. Anyway, if you're depending on such behaviour do have it in mind when upgrading your hub to 1.21 (and apply this patch also). It shouldn't affect anything else (other --force usage) as this is the only task running from builder and not directly via API.
This is an early warning - we're now testing that fix, so have an eye on the "testing-done" label before we can be sure that it works and it doesn't break anything else.