Entertaining to see them simultaneously claim 100% uptime in February and list outages both yesterday and today. If 'users can't send or receive messages' on a messaging platform, your service is down.
"When a measure becomes a target, it ceases to be a good measure"
I think in this case it's more, you can't be held accountable without oversight. You can't be held accountable to measures you define, measure, and report yourself without any oversight from anyone else.
What's also interesting is their carefully crafted language. They have "Slack is not loading for some users" listed everywhere instead of "most users" or "all users" and also "Something's not quite right" instead of "Something's not working" or "Something's wrong".
If you look today (one day after the incident) you'll see that the status page now shows only 3 9s of uptime for the quarter.