They tested the wheels with a 21mm Corsa CX... which makes the results even more surprising, since the Hed is the only one designed for wider tires. They did a sweep from 25 down to zero yaw, and the Hed was the only rim to have flow attachment at 15 deg... which resulted in a drag of only ~30g, compared to 150-200g for all the others. At 10 degrees things tighten up a bit, but the Stinger is still the best... and it's the best at every angle from 0-20.
Wheel, Drag @ 10 deg yaw (front wheel, 30mph)
Vision Trimax Ultimate, 175g
Cole T85 Lite, 160g
Easton EC90 TT, 145g
Bontrager Aeolus 9, 120g
Zipp 808, 110g
Hed Stinger 9, 85g
I see that Zipp has a new Firecrest 808, but this one was the old model.