So I was experimenting with a realm I had recently gotten, and was trying to bug hunt/ experiment with different world types. I had generated a 1.18 single biome lofty peak world, and wanted to see if I could upload it to my 1.17.1 realm. Turns out I could, and it some weird stuff happened. Of course, all the world gen was reset, but goats were falling out of the sky, over biomes they shouldn't normally appear in, like the ocean. Then I try uploading a normally generated 1.18 snapshot world, and the same thing happened: all the world gen was reverted, expect for instead of goats falling from the sky, there were polar bears. Also, when loading new chunks in the world, polar bears were still spawning. This isn't a huge bug, and will probably be fixed when the 1.18 generation has been fixed, but still weird.