I think its because Silkies can both be purchased from a hatchery under "Silkies" and they are also listed in the Bantam section as Silkies... they are the same size bird and they come from the same bin at the Hatcheries when they are shipped. Feed stores and places like Wilco and Tractor Supply Company mark on the boxes what they are told from the Hatcheries. Just check out their "Rhode Island Reds", "Barred Rocks" and "Americaunas"... they are not accurate. At least the Silkies are actually still Silkies.. even if they are usually very poor quality (but still sweet birds). Overseas they have two sizes and some people have been talking about importing the larger ones - but they will not be available from anybody except a breeder.
Kno of a breeder in oregon