I think the rule is pretty accurate although definitely not 100%. The vet told me that even though the parents are small, sometimes their genetics go waaay back to grandparents and they can be either larger or smaller. She said this often happens: The breeder gives an estimate between the parents' sizes and the buyer ends up with a puppy much larger than expected. Once they are at least 4 months you can get a better picture of how big they will be. No matter what size, we all love our little babies!
