I know the news caves are still in very early development, but I thought I'd share just a few things I notice when messing around in the newest snapshot. Namely, old cave generation doesn't happen below y=0, and the "cheese" cave generation doesn't happen above y=0. Both either start or stop directly at that point. The only cave generation to not have this limitation seems to be the "spaghetti" generation. I wasn't sure if this was a bug or intentional, but I decided to put this here just in case.
Also on a side note, the dripstone cave biome seems to not be fully integrated with the new y levels, as below y=0 no large dripstone block stalactites generate, even though plenty of stalagmites do.
Thank you for your report!
We're tracking this issue in MC-214843, so this ticket is being resolved and linked as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature to see if the issue has already been mentioned.
Also, dripstone caves do not generate at all yet.
Quick Links:
📓 Bug Tracker Guidelines – 💬 Community Support – 📧 Mojang Support
📓 Project Summary – ✍️ Feedback and Suggestions – 📖 Game Wiki