Floating Islands worlds created in any of the Badlands Plateau biomes are not Floating Islands

When a floating islands world is created and the biome is changed to "Badlands Plateau" or any of its variants (e.g. Modified Wooded Badlands Plateau), the surface of the world appears normal. Below approximately y=6, it appears different (there is open space as in the bottom of a typical floating islands world, no bedrock, and floating abandoned mineshafts), but the surface is normal. Additionally, the player sometimes spawns in a block. This occurs in worlds created in survival and in creative.