One of Greenough's basic design tenets is: "Straight rocker in the last half of the board. "
He can get away with this extreme design premise because the tails on his boards are flexible...so he can have dead straight tail lift and still turn easily. This is a luxury conventional board builders don't have...and the reason he developed flexible boards in the first place.
The straight tail Greenough has utilized since the late 1950's sets up the forward knuckle perfectly, because by default, the rocker break already has to occur in the front 1/3 of the board. So, the two elements fit together without a fight.
Another aspect of this design synergy is that the straight tail wants to push the nose down in the water, and the knuckle (in both the rocker and outline) resists the tendency to either catch or pearl.
Additionally, when in trim, the constant 'power-on' push of the straight tail results in a high overall rate of speed...