Yes that's a good thing. That means you should be able to move on with things and get referred to a GIC, and that people are taking you seriously. Hopefully other people will start to take you seriously now that you can say that you've been diagnosed officially as well.
You're also lucky that you got to see your letter, the only one I've ever seen I had to steal out of my dad's car. Half of them never even got sent to my parents.