I suppose they get whatever history tells them will sell in a particular area. I have never seen bantams at our TSC.I order large fowl from hatcheries since I want to know what I'm getting and I like getting good stuff in the mail.
I'd get bantams from the feed store since the minimum order on them from hatcheries is usually 20 or so and I don't need 20 or so.
This year, I wanted bantams and the feed store packed up chick days in June and didn't get any chicks until September, and of course they were bantams. I almost bought some but I was busy with integration with two batches already. Maybe next year.