Note to Bug Reporters: Please read the whole thing, as maybe part of it may be a duplicate, but then if you don't read the rest, you will mark it as a duplicate.

This affects 20w09a and 20w10a for the record. I decided to enter the Nether 4 days ago, and appeared in the so-called Soul Sand "Valley". It was not a valley, it was just a bunch of islands above an extremely large lava pool. This is not supposed to happen, because unless Soul Sand Valleys are supposed to be called Soul Sand Islands, then it doesn't fit within the biome.

In the 20w10a patch notes, Mojang says that there will be no more floating islands. I don't think so!!! I upgraded my world to 20w10a, and there were still islands, even my Nether Portal area is still an island.

I forgot to mention that I spawned next to a Nether Fortress. Upgrading to 20w10a, the land took over the Nether Fortress and some part of it disappeared.

Thanks for reading and hope you solve it!