This is rather interesting. In a crowd of people, or in a classroom, my child never had any emotional outburts. He showed no emotion at all, even when another child sunk 6 teeth into his leg. My kid never uttered a sound. He's always used suppresion and still does, which goes along with those "core symptoms" of autism. At home was a different story, home didn't consist of social demands.
I think those who have outburts in a social situation and those that don't or under react, defines the difference of those who truly have the core features of autism, and those that don't. Those who react, even if an outburst, is outwardly showing a reaction which is actually better than those who never do.