Fair point re an objective test, but the comparison was a metaphorical rather than direct comparison.
If there were no gender markers on official documents it would not validate or invalidate you.
Does your phone number have a gender marker? No. Do you feel more or less validated by this? I suspect you don't care. Of course we may find other things to obsess about but fundamentally I can see no valid reason for needing a marker on your official documents.
Of course police will say the suspect is a 30 year old male with blonde hair and green eyes... Do they need any of this on a passport to correctly identify someone? No. They look for someone fitting that description PHYSICALLY not based onwhat is on their identity documents...