uhh no its not, its encouraging him that he's doing fine. He needs to be familiar with making simpler sigs before going into an advance one.
I'm pretty sure that he won't get better unless you tell him what he needs to work on though.
its like telling a kid who is learning the alphabet, if you tell him "keep practicing" he will go up to a certain letter then stop. But if you say something like "Oh here is a new letter it is called 'q'." Then he will start learning that letter.
get were I'm coming from? :3