You can oversimplify the airfoil shape by saying it acts like a loose leech it doesn't really work that way.
Rather they took an airfoil developed specifically for foiling (looks like one used for the AC72 cats) which has a very stable center of lift. The original H2 has more lift per cm2 but the undercambered shape is notorious for changing center of lift with speed. This is that building of front foot pressure and eventual instability as speed increases.
Washout just softens the stall and reduces the chance of tip stalling which should help lock it in during carves/gybes.