I interpret this "you will be punished for wearing baggy clothing by secondary harassment" directive in exactly the same spirit that I interpret the directive that allows screeners to feel my breasts:

The perverts in charge at TSA haven't gotten enough jollies off of seeing people's bare feet and feeling women up. They'd like to see every curve of our bodies through our clothing. "If you're not willing to dress in a way that leaves nothing to the imagination you'll be sorry." Once they have us all frightened into spandex-only airport outfits it'll be that much easier to ogle the young women. This directive, like the others, will be unevenly applied to those young women that screeners particularly want to watch being humiliated and felt up in a public place.