Mojang removed "Trial Chamber Echoes" (ambient cave sounds) because Beta testers reported hearing phantom voices. Creepy stuff.
"The 1.21 Beta was chaotic, broken, and honestly? More fun than the final release. Should Mojang bring back Beta Overcharge for a limited-time mode? Let me know in the comments." Option 2: Blog Post / Patch Notes Style Title: Minecraft 1.21 Beta Retrospective: 5 Wild Features That Didn't Survive minecraft 1.21 beta
The Heavy Core originally had a 100% drop rate from the first Breeze in a chamber. People just killed one Breeze and reset worlds. Mojang removed "Trial Chamber Echoes" (ambient cave sounds)
First, the Breeze. In Beta, it had a 10% chance to deflect arrows back at you . Bows became a death sentence. More fun than the final release
"Remember when the Mace was so overpowered it could one-shot the Ender Dragon? No? That’s because Mojang removed it before the full release. Welcome to the lost Beta of Minecraft 1.21."