You are being very generous in calling it a bug at best, or willful ignorance going the other way with it.
A service provider always has the option of providing an SLA that's based on the true uptime of the underlying service without treating the dashboard as a definitive source of truth. Choosing to make the dashboard their official record of downtime means they're opting in to having inaccuracies in the dashboard qualify as fraud.
The reason providers don't want to update status pages is because it provides easy ammo for customers to say "look, YOU said you were down!" even if they weren't actually affected. It effectively greenlights an SLA lapse for every single customer.