It works at high AoA, not speed.
Hence pulling 'g' in an early Hunter, the inboard movement of the Centre of Pressure caused the a/c to pitch up. The saw tooth wing effectively stopped it; the later Mk 4s (I think?) had the wing modded - and the big engined Mk 6s all had the new wing with the notch and certainly had no pitch up vices! Set full power, pull to the buffet, then milk the flaps to 23 deg to increase turn rate.....