The size is for more toy / teacup size dogs. (chewy.com)
Mini Pitbulls aren't teacup size as you might expect - they are small but still very muscular dogs that look much like a Pitbull. (animalso.com)
That was the point I was trying to make about he pomeranian, yorkie and the other small dogs - they are already small enough to be considered teacup size. (pethelpful.com)