This applies only to the Buffet world type upon world creation.

The only differences I'm seeing right now is that, when you select The End or Nether in the Buffet's biome selection, upon loading the world you can tell that they are using stone instead of Netherrack or End Stone. Also, it is using the Overworld's clouds, sun, moon, and horizon instead of their usual purple or red sky. Kinda weird...

You should optimize the Buffet feature to give The End and Nether Biomes their own look.