Maybe, maybe not.
For TSC, the assortment is better than ordering single breeds, not just because it is a bit cheaper, but also because many people like to get multiple kinds (like you did) rather than getting that many of just one kind of bantam. Individual customer sometimes order assortments too, because they know they want a variety, but don't want to try to pick each individual breed.
For the hatchery, they have to count their chickens before they hatch and pre-sell them, so they can ship them immediately. But they don't know exactly how many eggs will hatch. So they make a conservative estimate, take orders for a certain number of each kind, and pack the rest as assortments (assorted bantams, assorted brown egg layers, assorted white egg layers, etc.) Overall, I think it works pretty well.