My DD is diagnosed with dysgraphia and her spelling is considered superior on her testing. She now keyboards for creative writing in school. This seems to be helping, although I think she still picks versus types unless it is in the actual typing program. It was explained to me that she can't concentrate on physically writing i.e. making the letters correctly and neatly and the actual mental writing. For my DD it has gotten more pronounced as she has progressed in school and more detail and thought is required in writing.
Her verbal skills are way ahead as well. She does have aspergers and this can impact some of her writing as well.