The bug

When looking at the diagram for ore generation I noticed how emerald would spawn commonly at really high Y levels, such as Y=256 but only in mountains.
After noticing this I decided to load up an Amplified world to see if emerald would spawn as high as it did in the graph.
However, while emerald did spawn as high as it said, it spawned much more rarely, and it would only have 1 ore per vein. If the data of the graph is correct, than it appears that emerald still has kept its original variety, but just spawns higher up.

How to reproduce

1. Go to a Mountain biome in either a normal or Amplified world
2. Remove all stone with a command (Such as /fill)
3. See how small emerald is in comparison.