Actually, the Wood Elves army book states that Enchanted Arrows are Enchanted Items. The BRB states that Magic items are considered unique - you can only have one of each in your army unless otherwise stated in the magic item's rules.
It doesn't actually say in the Wood Elves book that you CAN take more than one of each Enchanted Arrow in the army. It also does not say that Enchanted Arrows are unit upgrades. It says "The entire unit may take one of the following types of enchanted arrows..."
As Wood Elves players, we would love to be able to take multiples of some of the arrows, but some rules lawyers could argue that we can't. Until GW puts out an FAQ about it (or covers it in 9th Ed.) it's up to the players and TOs to work out among themselves.
A
