Every conversation I have I run every input someone says through a decision tree to determine what the appropriate response is. I do this in my conscious mind. I didn't realize this wasn't normal until much later in life.
Unless you're displaying a caricature of "happy" or "sad" emotional expressions I have no idea what your emotional state is. I'm completely blind to it. I have to consciously analyze the shape of your mouth, where your eyebrows are, compare it to the context, etc. to try to determine your emotional state.
Not only am I blind to other peoples' nonverbal communication I don't express my own naturally. Every emotion I express through non-verbal means is largely "acting" on my part. I have to consciously make my expressions match my emotional state.
My anecdote may not match exactly what another person's with autism, but that's the kind of difference that's meant by doing things "automatically."
Yeah, but it doesn't require the same amount of effort from everyone, and neurotypical children will eventually get it. It takes an order of magnitude more effort for children with ASD and in the most extreme cases, they simply can't.
It's like red/green colorblindness - some afflicted eventually manage to tell the difference between the same shade of grey, but for normal sighted people, the number inside the circle of colored dots is blatant and obvious, and requires no studying of the picture.
There are children with ASD that are highly-functioning and if they manage to get good grades, it's possible for them to escape notice. However, there are those for whom social situations simply don't make sense, and no amount of effort, self awareness, or peer feedback can enlighten them.
Especially things like smiling or crying to get something (depending on circumstances) etc - they do it before they have logic and before they have ability to plan. Two years old has tendency to do stuff adults around find cute and react to, but it is not conscious plan. Autistic kid won't or will to lesser extend.
It's kinda shitty to imply that someone is lying or delusional because their lived experience doesn't match with yours. There's plenty of literature on how autistic people learn socialization and how it differs from neurotypicals.