If you use a datapack that changes cave biome layout it will force the surface biome instead

in some places as if the cave biomes don’t exist in them areas

will upload a picture comparing the two 

make public after reading this

may be due to some intended limit to very the existing caves on the y axis

realy should be checked biomes only work right in lay out when no surface biomes exist in multinoise 

the all caves datapack has full temperature noise range lush.png shows an area were it does it wrong