What I expected to happen was the game to generate structures at least where it used to (villages in plains, dungeons, mineshafts, etc.), if not at more places (new biomes), when the option to enabled in world creation to generate structures.
What actually happened was the option was enabled, but no villages spawned in flatlands, nor did any under or above ground structures spawn in normal worlds (I explored far in directions and x-ray'ed the ground).
Steps to Reproduce:
1. Create a new world, with Structure Generation On
2. Explore
3. Find no generated structures
Can't reproduce, I spawned next to a village in a flat world.
Also, put the snapshot you tested this in in the affected versions, not "Future Versions".