The status page clearly states (when I look) that:
Incident on 2020-07-15 15:41 UTC We are investigating reports of degraded performance. Posted 9 minutes ago. Jul 15, 2020 - 15:41 UTC
Incident on 2020-07-15 15:41 UTC We are investigating reports of degraded performance. Posted 9 minutes ago. Jul 15, 2020 - 15:41 UTC
Recently, more and more of them take 10-15 minutes until they mention a service outage. I don't work in super HA, I don't want to get an alarm because a single ping failed etc, so I'm lenient and have a few minutes of a delay in alarms. If I'm writing an internal incident report before the official status page is updated, that's bad.
This seems similar: external users noticing the outage and posting on HN before GitHub notices & acknowledges it.