The goals “assuring folks that there is isolation” and “identifying flaws that need to be fixed” are somewhat contrary to each other.

The post-mortem should identify flaws in systems, processes, and thinking. It should not try to assure people that there is isolation when there is evidence to the contrary.

> You want to fix this specific issue, but also ensure that whatever process took down one DC doesn't affect other DCs.

This was a multi-regional failure. So, this specific issue is also an isolation problem, among other things. You will want to ensure that this problem doesn’t happen again but you shouldn’t assure that it won’t.