This is a crazy thought, but could those flags have been added to bows with the intention of going HAM on someone with the bow in melee? Think the way Neytiri uses her bow in James Camereron’s Avatar (by James Camereron) - if something gets close, she just goes ape on them using that tree-branch bow.
Seems like this should probably be handled the way bayonets and butt-strikes are, but it wasn’t really done properly by whomever made the bows.