The reason I didn't want to make them a different creature is because these are the ancestors to villagers, they look similar because of this. They give you copper tools and other uncraftable items is because you won't know the recipes they are lost to time. They give you this as a lore stand point. Because real ancient humanoids had copper tools, and copper tools is a frequently posted suggestion and I'm offering it to them. The reason why they don't accept emeralds is because if you time traveled to 1980 you couldn't take a 2000s currency because they'll think its fake. The player would want to thaw them out to get these uncraftables or new enchants because you can't get these conventionally in the modern times the game is set in. People also want renewable pottery shards, if you give them the shard they will replicate then them. It also is lore to the previous people who might know or were the ones who made these ancient structures. If you don't want to interact with them like the sniffers you can avoid them entirely. But since the battle hammer is like the trident someone will want it, these things will be more powerful as a reason to go out and thaw them.