My son and I were both DX within the past year. We are experiencing a pretty severe learning curve on the subject.
His therapist seems convinced that when my son appears distressed, he smirks from time to time. Usually this is when he is put in a situation where he is uncomfortable talking about something and is being pressed for a more appropriate response, usually close to shut-down. The therapist insists this is evidence that he is mocking his distress to get out of the situation, that he is being manipulative. All of the focus then turns to the goal of getting him to react appropriately and stop faking shut-down to get out of it.
I had the brilliant insight of actually deciding to ask him why a smile would sometimes flash accross his face in session when he is distressed. He told me at those times his mind flashes to something funny he saw in one of his minecraft videos. Since he can't escape the situation, he escapes in his mind.
I have no reason to doubt his account of things. This kid is not a good liar. And not a single bit of attention is paid to the fact that he is experiencing a type of distress that his therapist has likely never experienced. I'm convinced this therapist doesn't know what she is doing. She probably has a list of justifications for not having to consider what I or anyone else has to say (that I'm not objective, I'm bitter about my autism, or 'of course your son is going to lie about it, he's manipulative', etc.) Overall, they seem to be more interested in who's who than in what's what.
It's frustrating that they are not willing to test their own ideas. It's scarry because if I didn't know better, I could have simply believed her and my son would be pegged as having character issues instead of sensory issues.