I've had push backs on my postmortems before because of phrasing that could be constituted as laying some of the blame on some person/team when it's supposed to be blameless.
And for a long time, it was fairly blameless. You would still be punished with the extra work of writing high quality postmortems, but I have seen people accidentally bring down critical tier-1 services and not be adversely affected in terms of promotion, etc.
But somewhere along the way, it became politicized. Things like the wheel of death, public grilling of teams on why they didn't follow one of the thousands of best practices, etc, etc. Some orgs are still pretty good at keeping it blameless at the individual level, but... being a big company, your mileage may vary.