Stone can still generate with old lava pockets under y=0. I believe this shouldn't be case and deepslate should be generated instead.

 Expected result

Deepslate or tuff to be generated under y=0

Actual result

Stone can generate as well

Reproduction

1. Make a new world (or use an old one from the snapshot)
2. Find a lavapocket under y=0
3. See stone

I saw some issues pointing out, that infested stone can be found, but this is normal stone.