Minecraft wiki entry for Development_versions, associated text: The bottoms of hoodoos in Eroded Badlands biomes no longer make flat ceilings in caves underneath (MCPE-146984).
Lily Pads no longer get placed in aquifers under Swamp biomes (MCPE-125913).
Fossils can now be generate below Y=0, with Deepslate Diamond Ore Blocks instead of Coal Ore Blocks (MCPE-144065).
Fossils will no longer generate floating in caves or water.
Mineshafts now always generate above the Bedrock layer (MCPE-147575).
Biome decoration features in cave biomes now have similar frequency as Java Edition.