The thing about assigned sex labels (AFAB/AMAB) is that a lot of its usefulness comes from discussions around medicine (though there are still issues with this). In a social sense, AFAB/AMAB isn't very useful to describe peoples' lived experience.

Assigned sex happens to people as babies, and "AFAB" and "AMAB" describe very broadly sex categories. Assigned sex acknowledges past assignment, not current reality with regards to one's sex and/or gender.

I find that when people try to apply sex assignment to social settings (e.g., "all AFABs experience this!"), it comes very close not only to misgendering, but also to sex essentialism in many cases.

I simply think there are too many assumptions made about what every person AMAB has (such as a certain body, a certain gender, and certain lived experiences) and what every person AFAB has. We cannot make sweeping generalizations about people, and I think a lot of people seem to forget this especially with regards to transition and/or "rare" sexes.