Denmark made the military service mandatory for women too this year.

I don't know of any legal differences at this point.

There's still plenty of differences but not from a legal perspective.

Like, maternity leave is longer than paternity leave, but that's not due to gender, but rather who is pregnant. For instance if a lesbian couple has a child, only one of them can have maternity leave, while the co-parent gets the equivalent to paternity leave.

Also, men aren't screened for breast cancer and vice versa for prostate check-ups. I don't think that's done on a legal basis though, it's just a healthcare service aimed at different demographics. Anyone can request a prostate check or mammography and get it if the doctor finds it necessary.

Changing rooms at public swimming facilities are separated by gender, but they often also have a third room which is for families with small children, people with handicaps or anyone else who don't want to or can't use the public showers.

"Biological sex" says jack shit about a trans person's biological characteristics, especially deep into transition. It's more often than not a dogwhistle that transphobes use to imply that trans women have the same violent sexual tendencies as many cis men, and to imply that those characteristics are somehow immutable.

The state does not need to get involved in a medical discussion between a trans patient and their doctor.

Lol imagine going to a doctor and they can't figure out your gender if it's not on you legal documents.

Get another Dr. I think this one got his license from Trump university

The blood group is very important too, for medical issues, but I don't think it is common to make it a legal marker (such as on passport).

Also, some people are born not matching exactly the classical genders, and labeling them legaly male or female can be misleading for medical things...

Does it need to be tied to the legal system, though?

Everyone has a different anatomy/needs. You know how many random foramen and bones people can have? Random extra shit that the body spontaneously develops on it's own for no reason? Most of them are fine, some are not, but to say we need to know if you fit into the "male" or "female" box to treat you is incorrect. We need to know so much more. In fact, I think the mere presence of a vagina seems to tell a lot of doctors "Don't take this persons pain seriously," so I think if we just assume everyone is a male or a testosterone/testes-deficient male at the clinic, we might get better results.

The US does that on purpose. Read up on a barbaric practice called v-coding

maybe we shouldnt let prisoners sexually assault each other regardless of gender

Very true, so while we're at it let's abolish prisons.

That happens frequently in the USA.