Using the following preset has different results in 1.15.2 and 1.16. This seems to be the same issue as these from 1.13: MC-132362 and MC-131749

The preset:

minecraft:bedrock,200*minecraft:stone,2*minecraft:dirt,minecraft:grass_block;minecraft:plains;village,mineshaft(chance=0.8),stronghold,oceanmonument,biome_1,dungeon,decoration,lake,lava_lake

Screenshots - imgur link, I couldn't upload them here due to error (Jira could not attach the file as there was a missing token)