Which isn't realistic in some cases. For example, if the postmortem determines that project management was lacking, that traces back to somebody, even if he or she isn't named.
Occasionally individuals really are to blame. But organizations get better results when everyone assumes positive intent by individual employees and focuses on finding process problems.
Bill Gates formed a highly competitive internal environment. You were expected to stand up and fight for your cause - even against BillG himself. If you were right against Bill it was extremely good for your career. This was a time where the success of a BillG review was determined by how many F-bombs came out, and it was never zero.
For more information: https://www.joelonsoftware.com/2006/06/16/my-first-billg-rev...
Also understand MSFT culture has changed dramatically since that time. Its no longer representative of the company today.
Also keep in mind that Microsoft today is a robust corporation with many jealously defended fiefdoms; carefully picking the people to throw under the bus to protect your fiefdom and attack your internal competitors’ fiefdoms is an important skill set in such an environment. You could be seeing that in this postmortem, and that is exactly what people are trying to stop by keeping postmortems “blameless”.