Ah you are correct. I was looking the wrong stat, I stand corrected. Though why does a pure melee unit have BS 4 if they use halberds and are never supposed to shoot ?
Because they're elves and as such have a high ballistic skill. You won't find BS3 elves in our book just as much as you won't find high toughness elves (except Malekith).
When I think of something witty, I shall put it here.
Perhaps when they get upset they throw their halberds? Like in a temper tantrum.
Seriously, though, yeah it's because they are elves and retain the elf base stats. Otherwise you could also ask why Cold One Knights have a move stat (when they never use it) and probably a few similar questions.
"While all answers are replies, not all replies are answers. So answer the question."
Well, we will probably will lose A TON of magical items in the next codex, the hydra will be more expensive, so I would love a cheap spammable lifetaker XD.