The beauty of Murderbot being such an unreliable narrator in the books is that it is actually 100% plausible MB was hallucinating a self-insert Sanctuary Moon fanfic the entire time it was being rescued and left those details out of its narrative because they were too embarrassing.
I imagine that for MB, realizing it accidentally called Mensah “captain” out loud to her face like some star-struck ensign is a humiliation on par with a high school student realizing they accidentally called their favorite teacher “mom.”