AMAB
Assigned male at birth — a fact about a birth certificate, not an identity.
AMAB means male was recorded at birth. Like AFAB, it describes an administrative act, not who someone is.
It has real uses: medical contexts, and conversations about the specific social conditioning someone received. It is not a way of hinting that a trans woman is really a man, and being used that way is why many trans people treat it with caution.
The same rule applies: AMAB is something that happened to a person, not something they are. A trans woman is a woman who happens to be AMAB, and in most conversations the second half is simply irrelevant.