Brian Heywood, a republican millionaire who moved to WA from California to "escape liberals", has been abusing the ballot initiative system here using his wealth for years. He (and his PAC "Let's Go Washington") purposefully makes them misleading or otherwise confusing to understand in order to get them passed.

A silver lining is that most of his initiatives haven't passed (such as the initiative to repeal the millionaire tax), and those few that have over the years have been gutted, heavily modified, or found to be unconstitutional in the state supreme court. The supreme court here just became even more left leaning, and since the way he wrote the initiative makes it only apply to girls, it's likely to be thrown out.

It would require capturing a zygote.

Did you mean capturing a gamete? As in, a viable sperm cell or egg? Which proves that the individual is biologically capable of producing those gametes, which means they are capable of producing viable offspring?

Because capturing a zygote (a viable egg that has been successfully fertilized by a viable sperm cell, but hasn’t yet implanted itself on the uterine wall to become an embryo) would require a woman to have a fertilized egg. And I feel like requiring impregnation just to confirm sex is a little… Impractical?

It would mean positively identifying males would be impossible, because they’re not capable of carrying a zygote at all. That that’s before we even get into the whole “in order to confirm an elementary school girl is biologically female so she can compete, the doctor would first need to impregnate her to create a zygote” thing.