Glitchy Plains Biome in The Nether

I have spawned a new Nether Dimension. Here I find an ordinary nether, but when I travel far enough, I see a massive wall (I thought it was was the Far Lands for a bit, but they were removed ages ago and never looked like that). When I approached it, I found a wall of Stone. When I went up, I found a vanilla plains biome, complete with water, grass and caves (I discovered them in Spectator). There were also Zombie Pigmen in the ground. I have image proof in the attachments.