It would make more sense to me that when it comes to diagnosis, it is a very black and white thing.
One either is diagnosed to be on the Autistic spectrum, or one is not.
If one is on the Spectrum, one is officially autistic, when not, one is not, even when such an individual may exhibit some traits that are typical for autistic people or vice versa.
I may have been a little too nitpicky on choice of words, as I do understand when someone is called "mildly autistic", and I may say myself that certain people "have got it real bad", but when it comes to professional opinion and diagnosis, I doubt it's not a yes or no thing once the conclusion has been drawn.