I don't know about you, but I sometimes simply fail to notice some interpersonal cues, like I would be looking at someone's face and fail to recognize a face in the face - mild prosopagnosia. How would you even mirror... a shape that isn't a face for your brain? You don't. Also if someone doesn't make eye contact, it's not possible to mirror. I often find eye contact makes it impossible for me to listen, I look away in order not to lose track of the conversation completely, because I don't hear people all that great. I mean, I hear quiet noises and they drive me crazy or they jam the sound and make the conversation hard. One sensory issue on top of another. My brain isn't made for that kind of interactions, especially in groups or busy environments... Those are all apparently hallmark symptoms of the autism spectrum, so....