The Radial Dacron Sail Plan addresses the loads as they radiate from the three corners. Loads take the path of least resistance as do some sailmakers....
Many sailmakers will say that this is a flawed design but only because the typical cross cut is less labor intensive and uses less cloth, thus more profitable.
We Use "Balanced Weave"
Dacron  so the fibers are nearly as strong in the Warp direction as they are in the Fill.
The Lower third and Upper Quarter of the sail are radial to stress relief the Loads as they radiate, then the cross cut middle of the sail form is excellent for shaping and controlling the draft. The strong "Fill" fibers are parralell to the loads in that section.