Pouch of Flying Stars - Not functioning with shuriken?

Haven't really played since launch and have come back to check things out. I have an iksar monk running around Freeport, and I received an item called the Pouch of Flying Stars.

When I equip this pouch in my ranged slot my Mantis Star ability becomes unavailable. If I swap back to my Throwing Star Pouch it activates again.

I was wondering what was up, and after shouting soundlessly into the wind that is the Help channel I noticed that if I examine the Pouch of Flying Stars it shows the damage type is Crushing, not Piercing. Could this be why? Or is it just not something monks should be using? I can find little information about these items online (other than their stats).