What I expected to happen: new biomes will be added to previously existed. All biomes which the game can identify by their ID's will be created in MC worlds.

What actually happens: Frozen Ocean is still recognized by the game (e.g. when creating a new superflat world) but it is (seems to be) totally absent in normal MC worlds. Instead, Cold Beach happens by ice plains and other cold biomes. This is cool, however the possibility to create another, different biome ID=10 is not used any longer. An unused feature of the world generator may be found a bug. The expected Frozen Ocean biome could be vast areas of ocean covered with ice, also far enough from any land.

Extreme Hills Edge (ID = 20) is another biome which is still recognized by the game as such but absent in generated worlds. Resigning of Extreme Hills Edge is strange, especially that Jungle Edge has been added as a new biome.

Jungle Edge M (ID = 151) is expected to appear on borders of Jungle M and another, non-jungle biome. Instead, the simple Jungle Edge (ID = 23) is generated there. I have not seen a Jungle Edge M yet. If it generate at all, it must be too rare.

Biomes ID = 160 and ID = 161 have the same visible name, Mega Spruce Taiga. This is a bug because there is no way to recognize which one is present in a given place in the game. It is hard to say then if the biome ID = 161 (probably Mega Spruce Taiga Hills for real) generates at all or not. The Amidst program either cannot see it or it is so rare that impossible to find with eyes.

How to reproduce: examine a generated world in the game or with help of Amidst to look what biomes are in it and what biomes are absent.