Yeah, I just started a re-read (shhh, the todo list is still there, shhh) and I picked up on that - Breq says "Seivarden was easy, I knew she was male" but she says it one line after a Nilter has just gendered Seivarden, so it's entirely possible she's referring to picking up the Nilter's cue.

And that exchange with Strigan is so important! Because, like, if it was just "Radchaai are male or female but it's culturally unimportant" you wouldn't ask "how do they reproduce" - you might ask (as Dwarves get asked) "how do you tell the difference when it comes time to make a baby", but you'd only ask "how do you reproduce at all" if you're reading Radchaai as not having males or females AT ALL.

(I also love that Breq just casually implies that most non-Radchaai humans have access to, and use, the same technology. Because that's exactly the sort of thing that happens with gender! People get all tied up about what certain genders can or can't do even when it's blatantly obvious that they certainly can if they want to.)