Why are the ENIGMA Slalom and Formula booms that shape?

Bjorn Dunkerbeck and Steve Allen have been using these booms in PWA racing for the past 2 seasons. 

It allows for the deeper profile of the REFLEX without having to use a wider tail, which is heavier and can drag in the water.  It also keeps the rider very parallel to the sail and the extra width provides better leverage over wider boards.