Yes, I have encountered this problem quite a bit. I've also tried explaining it in a similar way without ever seeming to get the message across. Once I'm in the consulting room, the social rules are a piece of cake. It's always my turn to speak whenever the doctor/nurse stops, and the questions always require accurate, honest answers. Hardly any of the traits that make socialising difficult are brought into that situation and there are few distractions. I don't have to judge what mood anyone is in; only one person speaks at a time; sarcasm and facetiousness are less likely etc. etc.
I also think that because a lot of people feel anxious, are very tired, or are in pain when they see a doctor (why else would you?!), almost anyone is more likely to show slightly unusual body language, prosody and eye contact, so that autistic differences in non-verbal communication don't stand out so much against the "background noise" of stressed out patients dealing with discomfort.
The most recent CBT counsellor I saw was the only clinician I saw who really understood any of this. She had previously had some experience with autistic people, though it wasn't her formal speciality. She was the only one who immediately understood the importance of context and the idea of "masking". The counselling was much more successful with her than with any of the three or four counsellors I had seen before her.
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