Negative foot speed

When the lead leg (foot) passes the hurdle rail, is it a good cue to have athletes try to generate negative foot speed (paw back) or to just step down upon clearance.

I’ve heard fairly good arguments for both approaches at various clinics I’ve attended.

Interested to hear what coaches and hurdlers on this board have to say because I’m not sure which camp to join. Not sure if it even makes a difference, though I know if you try to snap down you get a reaction with the trunk going upright too soon resulting in some braking forces. But if the negative foot speed is achieved with just the lower leg in a somewhat subtle way just before touchdown, I can see where it might have some benefit in creating a more active getaway step.