I am with you that it would be nice to provide some sources. On the other hand, after spending time around math students, engineering students and other student

I am with you that it would be nice to provide some sources. On the other hand, after spending time around math students, engineering students and other students and in groups for students with a talent for math, these statements are obviously true. This is not a medical paper, as indicated by the phrase "on the spectrum", but everyone how has experienced these communities knows what the author is referring to. The best math teachers are not the best mathematicians, on average. I casually googled for sources for some of these claims: These studies do exist. But even if not, I would still think it is valid to talk about this phenomena (taking into account that measuring empathy, teaching ability or mass diagnosing large student bodies are difficult research tasks).