Why are self-stimulatory behaviors such as head banging not, on their own, diagnostic of autism?

Question

Quizplus · Accepted Answer

The Answer is It is not enough to simply use self-stimulatory behaviors to diagnose autism because it is one of the most
complicated areas of medical and educational diagnosis. A child must show six or more behaviors characteristic of the disorder for the diagnostic criteria of autism to be met. The required diagnostic criteria are used to rule out any other possible diagnoses.

Why Are Self-Stimulatory Behaviors Such as Head Banging Not, on Their