when Mobs are killed using a looting 3 netherite sword the loot drop rates dont seem to happen. in fact the only drop that seems consitent is rotten flesh from zombies, after killing close to 100 creepers 0 gunpowder was dropped. after killing 100 skeletons 10 arrows were dropped. after killing 200 cows no drops happened. I suspect this effects more mobs than those I have tested.