With this datapack, you'll also receive loot from blocks/chests/entities, etc., but you'll also receive additional loot along with the original loot. Each block/entity/etc. has a unique loot pool with 25-50 variations. It differs from mixed loot tables in that, while in mixed loot tables, you'd receive a specific item/loot randomly, here you'll receive random additional loot. The datapack can work on older versions, but the older the version (from 1.21.11), the more likely the loot will be corrupted.
