It seems, that it should work, but no filter is applied. E.g., when I go to: https://pagure.io/koji/pull-request/1322 and click 'testing-done' tag on the right side, I'm taken to https://pagure.io/koji/pull-requests?tags=testing-done which indicates, that it is the correct way to filter the results. Anyway, it just returns all of the PRs.
Metadata Update from @pingou: - Issue tagged with: RFE
Metadata Update from @jlanda: - Issue assigned to jlanda
Fixed on #4620
Metadata Update from @jlanda: - Issue close_status updated to: Fixed - Issue status updated to: Closed (was: Open)