Yeah I can see how that makes sense. All I can say is the old cliche "autism is a spectrum" line. Some of us are better at evaluating emotional states than others and it definitely requires some degree of self awareness that not everyone has. I'm not totally sure that emotional state carries over to behaviors anyway. Also if we're sticking to the popular perception of autism, autistic people are also supposed to be good at pattern recognition and I think that applies here. In sum, I think because of specialized knowledge and personal experience, the average autistic person would be better at spotting other autistic people than the average allistic person, but certainly there's a lot of wiggle room there.