Swooping Hawks and their grenades

[Tyrendian]

Hey guys, quick question we came across last game: Who "fires" the grenades Swooping Hawks drop when they arrive? Or, to be more precise: Do I use the Exarch's BS5 or the majority BS4? We agreed to use the better of the two - with the Exarch guiding the drop or whatever... but is there a definitive rule on that?
Also, just out of curiosity: Am I the only one who finds it odd that their grenades are not Barrage weapons? I mean, it's not like they throw them after they land... they drop them on descent, which to me suggests Barrage rules if anything does...

[Angelus Mortifer]

You nominate one model in the squad to shoot the Grenade Pack, so you get to choose.

It's in the Grenade Pack rule (p.66).