I don't know if this example is helpful, but here goes:
DD1 has lots of different 'impairments': behaviour, motor skills (both fine & gross), S&L (both expressive & receptive), learning, etc. etc.
Our Council is crystal clear that blue badges are not issued for learning disabilities or behavioural issues.
DD1's consultant wrote a form for our application on the grounds of safe walking. Both tendency to trip/fall & lack of danger awareness/impulsivity.
REJECTED
Consultant clarified on form that condition evidenced by MRI differences.
My appeal, along with the fact that DD1 trips/falls and stumbles, was that although some of her difficulties are behavioural and impulsive in nature, the cause of those difficulties is evidenced by physical changes in the structure of her brain on MRI scan. Therefore, I was appealing that it was not the symptoms that were physical, but the cause.
SUCCESSFUL.
With ASD, the physical condition may manifest itself in a myriad of ways, but it is nonetheless physical, whether that be structural or chemical.