Basically it's a feature which lets you add potion effects to swords. The effect doesn't apply to the player when they are attacked by a CQR mob wielding a vanta oiled weapon.

I tried spawning a vanilla zombie equipped with a vanta oiled weapon by console, and it doesn't seem to work with them either. Maybe you'll be better off just adding your own potion feature into CQR. It would open a lot of possibilities for dungeon creation if the npc menu had a potion section where users could define what effects the npc spawns with, as well as what effects they inflict with attacks.