I think he is adorable. I also think he is all yorkie.
I think sometimes the smaller yorkies kind of have thinner hair... But look at my Suri. She started out as a fat little fur ball...then had kind of thin hair...then had a beautiful coat coming in. Yorkies are funny because they change so much and you can never guess what they will look like. I bet your little man will be a handsome guy when he grows up, because he is just so adorable now how could he not be. :P