I keep Parker's short as well... I would find a new groomer if I were you. I've had Parker groomed ever since he was little, so I honestly wouldnt worry about them cutting his hair even though he is young. When I take paker I let them know that I want his coat short but not completely shaved, and that I like the tight yorkie ears and cleaned up around the face...I always walk away happy (even this last time, a new girl groomed him because my groomer is no longer with the "salon" I take him to) and she knew exactly what I wanted.
You just have to be firm with them and don't walk away with your pup until you are happy. Basically I would recommend you find a new groomer and let them know that you want them to use the razor on him to shorten up the coat without completely shaving him
Hope this helps!