Secret fourth option: It’s entirely probable, but most of Harrow’s traits that people relate to autism are traits autism shares with childhood schizophrenia. One of the main diagnostic criteria used to differentiate childhood schizophrenia from autism is the prescence of hallucinations, so lots of schizophrenic kids are diagnosed with autism until their other positive symptoms, like hallucinations, can be reasonably proven.
It’s entirely possible to be both, and many people are, but pointing to Harrow and just saying “autism” bothers me, because it contributes to the erasure of some extremely rare canon representation for a badly stigmatised and misunderstood form of neurodivergence.