that is a misleading way to put it - the reverse-thrust air does indeed move toward the front of the plane. it also moves outward, and is often taken from the sides of the engine, but a component of the (reversed) thrust is definitely going opposite the usual direction.

here is a thermal image of a modern jet with thrust reverses on : http://www.rusaviainsider.com/russias-mc-21-tested-for-rever...