And so what if they do? Nobody is throwing you in jail for selecting the "wrong" box. And if there is some special program you're defrauding.. well.. treating people differently on this in the law isn't part of my philosophy.
Yea, you can put down whatever you want on government forms. That's no mystery. Whether people at large accept you as that what you claim is on them. The government isn't an arbiter of reality any more than you are.
We are talking about gender here. Gender is only identical with sex if the person so chooses to identify that way. If you think that's "the way it's done now," you have been listening to too much conservative media.
The fact that you don't understand all of this does not speak well of you.
We're talking about both. Gender was traditionally identical to sex and this issue didn't come up much till relatively recently. Outliers, like people born with both sets of organs, were just that. To be consistent with this philosophy, race must also now be done as "whoever identifies as such". After all, it's just as much of a societal construct.
Something from within the last few decades isn't really archaic, that is generally reserved for (well?) over a hundred years old or older, and the vast majority of Lemmy users are either North American or European. Anglo/Eurocentric is going to be the relative norm on social media in general outside of specific apps, and those then trend East/South East Asiacentric due to their development origin. You should not be surprised to encounter this.
Heteronormative will also currently still trend as a default since over 80% of the population identifies as such. Intersex is also somewhere around or under 1% of the population. While gender and sex can most certainly be different, at least currently the supermajority of people will have these aligned and will use them interchangeably. This shouldn't invalidate or be used to discriminate against those that aren't heteronormative by any means, but something that is true 80-90% of the time falls within the colloquial or layman's qualifications for a broad assumption of "how the world works".
The fact that intersex people get to decide their primary sex (or more likely had a doctor decide for them at birth) on government forms is somewhat analogous to 3 wheeled motor vehicles that can be registered as either a car or a motorcycle depending on the State and/or county. This does not invalidate car or motorcycle as categories, nor does it invalidate andly other means of transport.
You can't use archaic as a preparative against one thing and then come back and use it as a positive for its "opposite". I read your link, it is a perfectly good link, so I guess your arguing that an archaic Indoasia-centric queernormative world view is "the way the world actually works" instead? If you think you can understand what someone is attempting to say/discuss by only half of an opening sentence, I understand why you seem to be arguing past multiple people in this thread.