Pushing blocks into ungenerated chucks can affect world generation

Using pistons to push block blocks into ungenerated chunks, it is possible to force the world generation to create specific structures. The exact details are very complicated, please refer to the videos below for more information.

Dungeons:

https://www.youtube.com/watch?v=9iaU1TvIQqM
https://www.youtube.com/watch?v=IITJsTbPvlQ

End pillars and ender crystals:

https://www.youtube.com/watch?v=EeobLrHkfYI