Minecraft wiki entry for Development_versions, associated text: Frozen biomes no longer generate Ice pillars below Y=0 on worlds with updated chunks (MCPE-125128).
Ocean ruins and shipwrecks are now generated in lower frequency (MCPE-143478).
Azalea trees no longer generate underwater (MCPE-125919).
Azalea trees can now generate in shallow water.
Rooted Dirt can no longer generate without an Azalea tree (MCPE-140867).
Vanilla Parity: Removed Deep Warm Ocean from biome placement (MCPE-147051).
Fixed pillars of Dripstone that could previously be generated on the surface of the Overworld (MCPE-139877).
Fixed an issue to prevent Small Dripleaf blocks from being placed inside Lava blocks.