She really was. She has an amazing essay that starts "I am a man." It is not about her gender identity, it's just a terrific feminist essay which is also about what society thinks of the elderly (especially women).

You see, when I was growing up at the time of the Wars of the Medes and Persians and when I went to college just after the Hundred Years War and when I was bringing up my children during the Korean, Cold, and Vietnam Wars, there were no women. Women are a very recent invention. I predate the invention of women by decades. Well, if you insist on pedantic accuracy, women have been invented several times in widely varying localities, but the inventors just didn’t know how to sell the product. Their distribution techniques were rudimentary and their market research was nil, and so of course the concept just didn’t get off the ground. Even with a genius behind it an invention has to find its market, and it seemed like for a long time the idea of women just didn’t make it to the bottom line. Models like the Austen and the Brontë were too complicated, and people just laughed at the Suffragette, and the Woolf was way too far ahead of its time.

So when I was born, there actually were only men. People were men. They all had one pronoun, his pronoun; so that’s who I am. I am the generic he, as in, “If anybody needs an abortion he will have to go to another state,” or “A writer knows which side his bread is buttered on.” That’s me, the writer, him. I am a man.

https://languagelog.ldc.upenn.edu/myl/IntroducingMyself.html

I also cannot recommend enough (thanks for the correction!) her novels The Left Hand of Darkness and The Dispossessed.

The former is about a visitor from Earth to a planet colonized by humans thousands of years before and those humans were genetically engineered to be hermaphrodites. It's an amazing view of a society that has no concept of either sex or gender.

The latter is about two societies- an ultra-capitalist society on a planet and an anarcho-syndicalist (anarchist/communist) society on an orbiting moon. She illustrates the positive and negative aspects of both societies, although the capitalist one definitely has more negatives.

Incidentally, she also has a series of fantasy novels about a world of islands called Earthsea. The first novel is about a seemingly normal boy who turns out to have magical powers, is sent to a school where you learn to be a wizard and ends up fighting the biggest threat to magic after becoming the most powerful wizard on Earthsea. Sounds familiar, doesn't it? Funny that it was written back in 1968. A certain well-known TERF was born in 1965...