The Bug
Creating a single biome floating world type or cave world type continuously spams "Empty height range: [136 absolute-0 below top]" non stop. Below is a zip folder of a log output created by just creating a floating island world type.
Reproduce
Launch the game with the output log enabled
Create a floating island world type or cave world type
Look at the output log
❌ Notice the non stop spam of "Empty height range: [136 absolute-0 below top]"
Can confirm.