You could phrase it something along the lines that he needs a little more practice with those things. Some kids are behind with reading or math and get extra time practicing those things. He needs to practice more with X,Y,Z. Everyone has weaknesses they need to work on. He finds it difficult to write at this time but he will keep working on it, and typing will help him to get all his great thoughts out on paper. I don't think I'd phrase it as a disability at this point. Just point out all his strengths.
