I think the Ursula LeGuin piece is trying to make the point that our default view of the world is "man". So she, and anyone else who isn't a man, are subtly forced into man-shaped boxes because our generic idea of what a person is assumes that they're a man.

I don't feel like the piece erases trans people. Many trans people are also not men and would have experienced the same issues that LeGuin has in relation to the gender default.