Upon death, only vanilla items are dropped. All modded items remain in inventory. The reason for this is that the datapack uses a list of items that do drop instead of a list of items that don't drop. Since the list only contains vanilla items, only they are dropped.
My suggestion would be to use a don't-drop list. I'm not sure if this is feasible, but it would be a much more robust solution if possible. It would allow modded items to drop, as well as making updating the pack easier when vanilla Minecraft inevitably gets new items.
Upon death, only vanilla items are dropped. All modded items remain in inventory. The reason for this is that the datapack uses a list of items that do drop instead of a list of items that don't drop. Since the list only contains vanilla items, only they are dropped.
My suggestion would be to use a don't-drop list. I'm not sure if this is feasible, but it would be a much more robust solution if possible. It would allow modded items to drop, as well as making updating the pack easier when vanilla Minecraft inevitably gets new items.