https://www.minecraft.net/en-us/article/minecraft-snapshot-21w07a:

Exception: Diorite and Granite and Dirt no longer generate below y = 0

https://www.minecraft.net/en-us/article/minecraft-snapshot-21w08a:

Andesite no longer generates under y=0

According to the Minecraft wiki, Stone patches would generate below Y=0, like Andesite/Granite/Diorite does above Y=0. Those patches are made of Andesite, instead of Stone.

What I expected to happen was...:
Stone Generates in patches below Y=0

What actually happened was...:
Stone didn't generate. Instead only Andesite generated, in these patches

Steps to Reproduce:
1. Create a new World
2. Go below Y=0
3. Look at the Stone Patches. They're made from Andesite, not Stone