Individuals smaller than the size prescribed by the standard are prone to genetic diseases and are more susceptible to various diseases.
Yorkies are variable in size. From puppies of one litter, one dog weighing less than 1.8 kilograms can grow, another one weighing 2-2.5 kilograms, and the third one is a giant weighing 5.5-7 kilograms.
If you want to have an obedient dog, take the time and money to raise it from an early age.