As it should be. The purpose of post mortems is to prevent future incidents, and obscuring the facts of what happened by removing names detracts substantially from clarity of understanding and, therefore, defeats the point.

There are two important things that make something blameless: phrasing and culture. If you've phrased something in such a way that there's a clear value judgement, your phrasing isn't blameless. And if you're writing in a culture where, no matter how precise the phrasing, the simple existence of a name will make people blame them for what happened, then your culture isn't blameless. Both are required for a blameless post mortem.

Also, think of it this way: no amount of anonymization will prevent the people involved from knowing who did what. If they're privately blaming the person for the incident, it's still not a blameless post mortem.

No amount of verbal wallpaper can fix a broken culture.