Out of sheer curiosity I tested this developer with a test clip contact exposed through a Stouffer wedge. I have not scanned in the clip, but from looking at it I'd say that with 5 Minutes development at 30°C the clip is seriously overdeveloped. We have every reason to believe that the alleged speed increase is an effect of this overdevelopment.
Alan, can you confirm that you used anhydrous form of Sodium Sulfite and Sodium Carbonate for your test? I did and seem to get significantly higher b+f density than what you showed here.