G.B.
Most toddlers at that age are still using the shoulder joint to move their arms and hands. They may have well developed fine motor skills in their hands but the arm muscles are still growing and developing. For example, you may notice while they are coloring they aren't using their wrist and elbow joint but the movement is originating from higher up, the whole arm is moving instead of just the hand. Drawing things like faces is just a circle, ovals, and putting them together to look similar to a face. They may not expect him to actually draw a face but to assess his ability to follow instructions, to put shapes together, all kinds of things can. Here are a couple of links I found.
http://www.babycentre.co.uk/toddler/development/physical/...
http://www.childdevelopmentinfo.com/development/devsequen...