My 2 cents while I continute to watch the circus catching fire.
- Yamato is stated as a woman by the Vivre Card. When Momo asks her name, she says "I am Yamato", not "I am Oden". Very important to notice that Yamato KNOWS that she's YAMATO, not Oden.
- Considering the traumatic life Yamato had, willing to impersonate some other character, in some kind of defense mechanism, is not something unusual. Or did you all forget about Sogeking? The difference is that, here, Yamato chooses to impersonate someone of different sex.
- We barely know anything about Kaido as a character. Or he has going for him is the "strongboy" thing. We lack information to know why he indulges Yamato's idea of "becoming" Oden. Is it out of respect? Is it out of spite? Imagine if we had development for Kaido during the arc instead of panels of 4Tricks and Hamlet. Wouldn't it be something?
- Oda's not really the most "woke" dude ever. Just see that every "non-straight" character is basically a sex deviant. (the entire Kamabakka Kingdom forcefully trying to turn Sanji into an Okama and bringing sexual innuendos at every or so line of dialogue, etc). So there's a great chance that Oda indeed wants to make Yamato a trans-male, but he doesn't fully understand what it actually means and goes for some oversimplification of "he just says he's a man as Oden, so it makes him a trans-male. Easy, ggwp".
- This last point becomes less likely when we have a character like Kiku, that CLEARLY says she views herself as female in heart, dresses in more feminine clothing, etc. She doesn't do it because she wants to imitate some random woman she admires. She does it because she identifies as a woman and that's it. Not the same thing as Yamato. Yamato identifying as a "man" is entirely tied to Yamato trying to impersonate Oden. If Oden was a potato, Yamato would be screaming she was a potato as well. I think it's plain disrespectful trying to say that this is the same thing as Kiku's case with the current information we possess.
- Lastly, Yamato is joining and is not dropping the Oden act anytime soon. Get used to it.