well... When I looked for my first yorkie, I also asked about that. I asked about parents, how big was puppy at age at 12 (I didn't speak with breeders who sold their pups in 8 weeks). Yes, I wanted a small yorkie, so the size was important for me. But not the size ONLY, of course.
However, I even didn't go to see puppies, who were TOO small. For instance, 1 ++ pounds at age 12 weeks. LIke I told already, 4-5 pounds I like the most