If you are to believe the stickers on the bus stops (in EY) “livgadim tzmudim tzarot nitzmadim” and “Bnot tznuot mon’ot asonot”
My take is that when we hold the BY and other girls to one standard, and everyone else to no standard, the tnius train has jumped the tracks and crashed. An indicator of such is the phenomena of ychidos segula going to the opposite extreme, long skirt, jacket, and poncho cloak, and I have also seen some getup approximating a burqua. (in Yerushalayim)