The idea is that it will allow players to use all their Trial Keys they get after they use up the Vaults in the Trial Chambers.
Since each Vault only opens once per player, you'd end up with a lot of extra keys in a singleplayer world (or even multiplayer). This should hopefully help with that.
To open a Loot Bundle, you need to have it's required Key. For Vault Loot Bundles, it's 1 Trial Key. For Ominous Vault Loot Bundles, it's 1 Ominous Key.
The code behind it is really simple and easy to edit, which should hopefully allow other people to add their own Loot Bundles with add-on datapacks (and let me add to the project with more loot tables in the future)