I know neurotypicals who stim, most notably my favorite aunt. She in no way comes close to fitting the criteria for ASD; in fact, she is about as NT as one can get, but she loves to rock and bounce her legs. She says it's relaxing. One of my NT students rocks from side to side; she says it helps her think.
I don't think that any one feature of ASD is exclusive to the spectrum. A diagnosis made when most of those features are present at once.
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"If you can't call someone else an idiot, then you are obviously not very good at what you do."