Question about Archer bonus'

[Keneth]

Well if you were concerned about which I could have told you that long ago, says right there in item.txt

filter {
  belligerent=ally
  unit=archer,bowman,cannoner,catapult,elf,elf2,goblin
}

We're just discussing why they made such a selection, they probably considered how the item fits, hence the scope only affects medium-sized humanoids, anyone else couldn't use it.