Or...maybe...by having them come in already being called by their correct pronouns,we highlight how much of a non-issue it ought to be? No one on TOS ever talked about Uhura being Black, which arguably did more for inclusivity than pointing it out nonsensically in character.
You might call me biased becaue I'm trans myself, but the way I see it, instead of a huge dramatic scene with Adira's feelings being hurt and them giving an impassioned lecture to an embarrassed Stamets about how respecting the identities of others is important, it was treated as a matter of a simple misunderstanding, rectified as quickly and matter-of-factly as possible. My reading is that it was treated as much as a non-issue as it could've been. Adira being a teenager, it is perfectly in character for them to take a while to figure out their identity and on what terms they want to go public about it, if they want to.
And if we want to compare Adira specifying their preferred pronouns to Uhura feeling the need to disclose she's black, we need to keep the term
visible minority in mind. Adira's gender is not visibly apparent to the uninitiated unless they directly disclose it themselves, which makes it a very different case from Uhura and the color of her skin or a Muslim Starfleet officer wearing a hijab as part of her normal uniform.
They can, but in this specific case the writers decided to sync up the experiences of the actor and the character, for greater verisimilitude. So Adira decided to use They/Them pronouns, and then tell the crew shortly after Blu did the same publicly.
It would require some connecting the dots, but I find it very telling that Adira came clean about their gender identity
after unlocking the memories of the Tal symbiont. I'm not arguing that being joined made them nonbinary, rather that they obviously had so much going on that was repressed, that I find nothing surprising in them only coming out as nonbinary after the dust had (largely) settled, Gray stowing away in their mind aside.
I'm not sure why that would make a difference. Can a person not play NB if they aren't NB themselves? Jessie Keitel isn't NB, but she played one on SNW.
Jesse Keitel is a fringe case as she still identified as non-binary transfem when she was cast for the role (and possibly during filming as well), only coming out as a trans woman during SNW Season 1 being aired. But transgender is an umbrella term with gender being a spectrum, so a nonbinary actor playing a binary trans person or vice versa is still okay as both fall within the trans umbrella (case in point, Ian Alexander is nonbinary but plays a binary trans man). The point it becomes controversial is when a cisgender actor plays a transgender role, especially in an economy where trans actors are already struggling to find roles.