Minecraft wiki entry for Seed_(level_generation), associated text: It is possible to generate Legacy Console Edition biomes on Java Edition version 1.7.2 - 1.12.2 by modifying the source code to remove 2 hard-coded layers in the biome stage of biome generation, which downscales the biomes 4x to obtain the final Legacy Console biome map, as the 1.12.2 old Customized's biome size option uses a different hard-coded formula to downscale/upscale biomes. Specifically, legacy console edition does not scale the biomes 2x immediately prior to where the biome edges are applied, whereas Java Edition customized changes the number of times biomes are scaled after beaches are placed on the biome map.