It's not a forced binary. There are no in-between gametes. There are large gametes (eggs) and small gametes (sperm).
The law and government doesn't get to decide this, as you say, it just is. How the law reacts to the scientific fact of the sex binary is a different matter.
The law and government doesn't get to decide this, as you say, it just is. How the law reacts to the scientific fact of the sex binary is a different matter.