It couldbe that what is meant by the black bounce s that black is relected onto the subject, not light.
For instance, when doing a portrait or a nude, and you want to accent the edge of the figure, you can literally bounce black onto the subject by placing a black gobo or wall as close to the subject as possible, but just outside of the frame. I've used this technique when doing leg shots for pantyhose ads. It adds some dimension to the form and looks quite nice against a white or gray background. It can also be used for portraits (usually of men) to add more drama and increase that "chiseled features" look.