The issues are around semantics of the words 'gender' and 'assigned.'
Assign is problematic as alongside being used in this context, it also means:
allocate (a job or duty).
appoint (someone) to a job, task, or organization.
designate or set (something) aside for a specific purpose.
attribute something as belonging to.
_
classify (a person) as having a particular sex or gender, especially on the basis of their genitals_ at birth.
transfer (legal rights or liabilities).
1 another term for assignee (sense 1)."this agreement shall be binding upon the parties and their successors and assigns"
I can see why trans ideologues then revolt against being told they are almost contractually obliged to follow gender stereotypes - except this phrase appears to have emerged somehow as a part of trans ideology.
It also sounds like the individual starts at birth, which is where the op is saying the mother is erased.
I see it more linked to futuristic ideas of manufacturing babies in incubators.
But gender ideology and liberal feminism reduces women to incubators via language and surrogacy.