It does not work in any ability. You have such perks in Athletics, Riding, Throwing. It also does not work for bows/crossbows.
I suppose it is turned off because of technical/graphical issues. If you look at your quiver you will have exact amount of ammunition. Now if you combine all perks you will end up with +3 throwing weapons but the in-game models do not contain model for additional projectiles ( this is my point of view on this issue ).
However I can't see this problem in the known issues, this is very easy to replicate.