Secret Near Lusuco?

So, today I was running around this place above Lusuco when I came across this strange overhang. Its coords are -120, -290. In it, there's these strange pots, and in front of it, there's a cream/white carpet.

It's a hopper. If you throw an emerald into it, it doesn't do anything. But, almost any other item will throw a snowball at a wall, opening this strange hallway.

Notice the prismarine and the button. If you go and press that button, you're teleported on to that block of prismarine, and this comes up after a second of blindness and colorful potion particles;

I want to say it's some sort of secret, since I've already completed ??? and Lusuco doesn't come in anywhere in that quest. Problem is, what? Something to come, or a part of something else?

 

Its been found before and i thought it was taken out?

 

Aka Ohms's lab
fu name

 

It’s basically an incomplete Easter Egg by Selvut. Don’t expect it to come out until... ever.

 

nicefind.oldmeme/poorattemptatlampshade

 

Big oof

 

Ct plz confirm