I think he's asking WHY they now race windward-leward vs. the old Olympic Course (ABCACA). That changed when the Spinnaker showed up. If you have a spinnaker boat, a straight downwind leg is much more challenging than a reach to a B mark. I don't know what the A cats like to run, since they don't have kites, but in any case a leeward leg offers many more passing opportunities and is trickier than a broad reach. That's why they got rid of the triangle.