Adira tells Stamets their pronouns, and Stamets says “okay” approvingly. That’s it. That’s the full extent of what you are calling a “big deal.”
You understand that even in a society where everyone is allowed to “just be,” accidental misgendering is still going to happen and corrections will still need to be communicated, right? Marco misgendered Nico on their first appearance, so Nico must have corrected him. You are effectively arguing that enby representation is only acceptable if actual conversations about gender occur off-screen.