Besides, it's not really a difficult secret to keep. Most Moclans probably don't want to know if they were born female because of the social stigma associated with that, so they don't go looking into the matter, and even if someone were to present them with evidence of the issue, they'd probably go out of their way to avoid looking at it.
Especially when you compare that to Discovery, which after two episodes has failed to sell me on any of its characters or even make most of them stand out.Notice how we ARE talking about these things seriously? How we're not still learning names (like one character in the pilot)? How we really are interested in Bortus and Alara and where they come from? After only 3 episodes, this show has worked its way into our hearts. I think that bodes well.