*cracks knuckles*
Julian Bashir was born autistic, and after undergoing genetic augmentation retains several autistic characteristics but no longer perfectly fits the diagnosis. Because of this he never received any help or guidance with his autistic traits.
The alien doctors who performed the augmentation were not experts in human autism, so to them Bashir looked as though the augmentation was a complete success. His parents were so thrilled with the change they did’t allow themselves to acknowledge they didn’t get the son they paid for. If they had they undoubtably would have taken him back for more “fixing”.
Julian himself doesn’t know.
Also the way genetically enhanced people are treated in DS9 by society is as if they have “sci-fi autism” anyway