
the modern Pom was bred down in size from what is essentially the German Spitz, which now comes in different sizes. some features like coat and body shape were emphasised by breeding and nd also grooming.
A puppy farmed Pom is likely to be bigger and throw back to the original as the bitches would be easier to whelp, have bigger litters, and no selection for Pom traits would e practised, if anything only those bitches that bred larger litters easily would be kept, hence the increase in size.
A good coat wouldn't' be an advantage to a puppy farmer either so no notice would have been taken of this or any other traits desired by a breed enthusiast.
Pom and other toy breeders often keep the larger bitches for breeding only and mate them to very small males to get show standard for the ring, but have bitches that can breed more easily, as the tiny bitches could have problems.