As you know that dropped item is heavily related to the next content that isn't made yet. They don't want to finish that item yet as it will commit to some decisions they aren't ready for, and if they did it would restrict some properly informed creative decisions on the next biome.

It would still be disappointing if you got an item that did nothing and was named. Would having it be named really change the way you feel? That's a very minor thing. The only reason that the item exists in the game at all is so you get the reward for beating the boss eventually when the next major content update drops.

Also, don't you get a trophy to mount for a new skill? I don't think that's 'basically nothing'. It's all the other bosses gave, as well as the item linked to the next biome. The plains boss also gave a placeholder item pre mistlands.