I'm always impressed when people actually apologize instead of dancing around an almost apology.
Overall this is one of the best post mortems I've seen - great tone, very well written, super informative, has all of the steps (apology, information on issue, real steps to prevent it happening again) that hurt customers generally want to see. Really impressive timelines too - 43s reconnect after initial issue, 15 minutes to change status.
Gitlab overall seems to have more incidents like this and I really like their custom of working through them in public Google docs. Definitely seems a better idea for incident communication than relying on your own tech (github pages) for incident communication.