That's not seriously the real engineering portmortem is it? That looks more like a 'Resolved the issue' update - it is way too shallow and vague.

If this was sent out at AWS as a COE (postmortem), it would be ripped apart - it is not going to satisfy anyone reading it that they should have confidence this class of failure isn't going to happen again. It looks like they haven't even identified the root cause(s) of the failure...