Thought I'd point out that the description for thrown weapons says a volley is up to 8 thrown weapons, but the game actually only uses up to 7.
Also, if you have between 2 and 7 thrown weapons in hand the feat won't let you throw all of them - you get left with one last thrown weapon in hand. Personally I'd rather it used all of them.
I'm guessing this is all related to the same bug (an extra -1 in there on how many missiles to use), but that's just a guess.
Tested in 1.04a Beta