Decided to check out the new Biomes, and I was seeing what the top of the world would be like. This is what I've found. It's not game breaking but I pointed it out.

Video: https://www.youtube.com/watch?v=h05MVqYG5fQ&feature=youtu.be (The mp4 was too big to attach)

Edit: Turns out that even water pools, Pillager out posts, and ruined nether portals spawn aswell. I went into the nether and the same problem appeared again, instead only mushrooms were spawning. made sure to attach those.