Cwesto, it is for
preventing hermi's. (For your next grow, this will for sure help you with m/f/h ratios) I believe that you spray it on the 1st and 3rd weeks of flowering to ensure that no male pods grow on the plant. No male pods = no hermi's.
You know what would be an interesting experiment?
Spray Dutch master Reverse all over a male plant. What would happen? A seemingly sex-less plant? Hmmmm.....