The QuebecCRV document shows an instantaneous peak of about 70% rear torque on a CRV. This quickly drops when the front ones get traction (in an acceleration from stop case).
If all 4 wheels are on the same slick surface, I don't see much point in intentionally spinning the front ones. If the rear ones don't have any more traction, they aren't going to get you moving. And the spinning ones loose all directional control. If there is side slope to the road, the spinning front will drift to the side.
On a hill, the rear might have better traction due to a rearward shift in weight. On some surfaces a spinning wheel might break through the surface ice, and gain traction that way. But on an all-slick surface, the best bet is apply equal light torque to all wheels, so the total torque is enough to get you moving, but the torque on anyone wheel isn't enough to break traction. There's where a symmetric awd system could have a real advantage (open diffs all around).
I've mentioned a test case where I got the E going from a stop on an ice hill. As I gently played the gas, I could feel one wheel, then another, momentarily gain traction and then loose it. Evidently, if a front lost traction, it would spin a bit, sending just enough power to the rear to nudge the car forward, allowing the front to regain traction. In was, in an intermittent fashion, imitating the 'equal torque all around' system.
