If holes in the bedrock are at height y = 0, after upgrading to 1.18 a hole will be generated to the next cave (or all the way through the world if there is no cave below).
If holes in the bedrock are at height y = 0, after upgrading to 1.18 a hole will be generated to the next cave (or all the way through the world if there is no cave below).
This is intended. If no bedrock is at y: 0 it will not generate anything below it. This was mostly done for skyblock worlds