I think their point was that having the trans at 10 degree's and the pinion at zero, actually made less power then having them at 10 and 10.

Clearly having both at zero would make max power. But as many have pointed out, sometimes it hard to change the trans angle. Looks like this is at least one example where equal and opposite angles made more power then just focusing on getting the pinion to zero.

My guess is the harmonics rob more power then the equal/opposite angles.