Do you really think Julia could cut her hair, bind or remove her breasts and look like a man enough that she would not be the target of sexism? I doubt it. And even then, she would be the target of toxic masculinity and gender policing. You know, the same circumstances that gets pre-transition trans women and gay men beat up and killed on the regular.
Then there’s your flawed analogy. It isn’t like calling yourself Chinese after visiting China. It is more like being born in China (or even born to Chinese parents elsewhere) and then brought to the U.S. when young, then visiting China again as an adult. Most other Chinese people might think of you as American, but you are still Chinese. for the most part, though, ethnicity is not a great thing to compare it with. If I was of mostly European heritage but born in Shanghai, would I still be Chinese?