Finishers!? I earned a few in Apex packs and now I need to unlock them?

you seem to be mistaken on which finisher move you unlocked in the apex pack. if you got it in an apex pack . you don't have to craft it. it just unlocks. same goes for all items.

some unlocks are universal to all characters like gun skins. and some items are character specific, like finishing moves and character skins.