Reading "The Left Hand of Darkness" by Le Guin, did she forget about the singular "they" while writing this?

It just seems incredibly odd for there to be so many lines in a book about gender insisting that there is no way to refer to someone (in the English language, at least) without implying gender. She even mentions the possibility of using „it“ at one point!

I’m liking the book otherwise, but every time the narrators ponder about pronouns without even considering „they“ I have to ask myself if there is any point in ignoring it or if she genuinely just forgot. I don’t think it’s possible for her to have not known about it considering how well-read she was and how long it’s been in use.