The reason why it's like this is because it's not like batraal where you just beat the boss and get loot. For ifrit, you not only need to beat the boss but you also need to be in possession of an Inferno Lamp key item. If you have a key item, you are allowed to loot the chest. If you don't have it you can't loot the chest.

In order to avoid people getting loot who didn't have the key item, the loot goes straight into the inventory of players who were able to loot the chest. It's exactly like Faction NMs, where only people who had the leve could get loot. However, the end result loot from faction NMs was tradeable, so it wasn't really an issue.

What they ought to do is spawn more than one chest, each that contains only one of the weapons. Then the player can choose which chest to open. If you didn't have the key item, you can't open any chests.