We're unable to obtain deepslate coal, and emerald ore while using Caves and Cliffs preview datapack, as both of said ores don't generate below y=0. Previously issue only occured for emerald ore due to its generation, but now, when deepslate blobs at y=16-0 have been removed, it is impossible to obtain any of those 2 ores in deepslate variant. I consider this a bug, because since 21w17a they're obtainable in vanilla worlds.