“Zona? Hyperbole such as this simply turns people off. “
That is exactly what I think. Equating a schoolgirl who wears a shorter skirt than you believe to be tzniusdig (covers the knees, but might not when they get into a car), or slightly above the elbow sleeves, with an actual hooker, is not just hyperbole. It is exactly the thing that causes some girls to believe that tznius is all nonsense. A zona is a zona, and not a young lady who dresses in a way of which you do not approve, but is surely not slutty.