Giving it a quick think with the people I know (given that I don't know the mental health status of people without diagnoses) it's an almost perfect split.
A secondary wonder comes in due to the theory of mind deficit that can come with those disorders - thinking, or guessing, that other people have the same information you do even if it's not been communicated https://en.wikipedia.org/wiki/Theory_of_mind
Maybe sprinkle in some illusion of transparency too https://en.wikipedia.org/wiki/Illusion_of_transparency
Of course there are a billion other variables, just a possible pattern that popped into mind as I was reading the article.
It could just be that people who socialise less in general are more likely to become guessers possibly (Caveman programming: If you ask for something and get rejected you are risking your position in the tribe)