Those averages are really low. My pom mix is 14 pounds, My silky terrier (related to yorkies) was about 12. Neither were/are overweight. Healthy full size yorkies and pomeranians should be closer to 10-16 pounds. Your mix is not all that much larger than those breeds and with a little cocker and pitty it is not surprising at all.
In recent years people have been actively trying to breed teacup sizes of dogs that were over 10 pounds and I am guessing that has effected average weights by alot.