For me ASD/Aspergers vs SA is a tricky one. I have moderate to severe SA. I was always introverted and shy but it tipped over to SA due to negative peer reactions to my physical/social awkwardness. Hence the physical/social awkwardness that could point to ASD(traits?) certainly preceded the SA.
I think it makes sense for a lot of people on the spectrum to wind up having anxiety. When it is difficult to read people, but other people can easily read you, and some people have bad intentions… of course that is a recipe for anxiety, in my opinion.