Originally Posted by polyspheric
If it's really anti-reversion, those small steps are actually triangles with the edge pointing down.
If they were symmetrical, it would reduce flow in both directions.
As I understand it, the 'rings' in the throttle bores can help shear along with the exit edge. The extension of the throttle bores into the plenum act as anti-reversion because they aren't an 'ideal radius' for flow in the direction of the boosters.