I legitimately want to know, because I don't know what to say here.
It's more like a 10 dimensional space, at least, with each dimension being a symptom or needs category. For example, I don't think anyone would diagnose me with autism, or even old asbergers, but I have a lot of sensory issues and struggle to parse speech and faces.
If you are aware of someone having some form of autism, and you want to know more about "where on the spectrum" they are, simply talk to them, ask what they struggle with, ask about their needs. If you didn't have to talk to a family member or nurse before talking to them, they probably don't need huge affordances.
Light is a spectrum. The frequencies composing a sound are a spectrum.
A volume control is _not_ a spectrum.