Arguably the other phrases overcommit though - Are they down? Are they up but giving bad data/intermittent? Are they up but there is a problem between the server and user? Are they up in some regions but down in others? are all covered by experiencing outages, but "are down"/"are not working" are more definitive, both in that the service is definitely not working and that the problem is definitely on Apple's end.

"Are down" can also suggest that the downtime was deliberate.