ZI did a write up following the Tiny races and he concluded it's definitely not working as planned. He noted one rider sling-shot past at 543kph
He didn't think the pack was any slower, and he also noted that if you wasn't at the front end of the pack then you were working very hard just to stay in the draft and easily dropped (probably what Hivey was complaining about as drafters like him tend to sit way back in the pack under PD3 for maximum draft/minimum effort).
I think the idea of what they are trying to achieve with PD4 looks good, it's just they haven't got there yet.
What I'd love, and those who used to ride on Bkool will recall, is the reduction in resistance when in draft (so you could feel less effort was needed to stay in the draft). This also meant if you put you nose in the wind, you felt the resistance change ... that in itself could effect the blob and stop the surging to the front. Drafting was one area that Bkool got spot on