^It’s hilariously bad community work to just bluntly tell people that “Non-binary” isn’t a gender. And then link them to the entire GDPR text without even doing the bare minimum to link to the appropriate chapter or section.
You don’t need anyone’s gender—not even from a technical standpoint (this account in particular was created through a third-party SSO and didn’t provide a gender, and yet your system didn’t complain).
You’re just greedy.