Actually, that's not quite true. I thought the same thing at first but then I learned.
When you drag a pattern into a folder that contains none yet, watch the little red line as you drag it. If the line runs all the way across the list window, it won't drop in a "sub" folder. It will drop back where you got it from.
If you crowd the right side of the list window when dragging you will see the line change from "all the way across" to "halfway across" the list window. That indicates you're going to drop it in the "sub" folder.
I was bent out of shape by thinking the same all of you are. Just happened to see it do this one day and PRESTO! I learned. Works every time.
Hope that helps folks.