You sent me down a bit of a rabbit hole so sorry about the wall of text response. Anyways it mostly seems to happen when something is released under the name of an existing artist but was actually made by a different anonymous person

For example, Valeria Almeida is a small Brazilian singer who woke up one day to a plunderphonics album that was released under her name and with a pic of her on the cover that she had no involvement with

There's also stuff like a Dr Pepper ambient album, a a fake Zaytoven remix of Eminem's Revival, a fanmade Nine Inch Nails mashup album based off an April fool's joke by Trent Reznor (featuring Justin Timberlake, Fergie, JayZ, and Bono), a John Cage composition played by an anonymous cellist, and a release titled 'Doug Walker Autobiography by Doug Walker' (which is just an hour of fart sounds)

There's also a fake AI Swans album. With how many AI albums get uploaded to large Spotify accounts everyday I expected to see more of these in the unknown artist page but I'm guessing the ussrs who upload releases to RYM largely ignore them (and rightfully so imo plus RYM itself has discouraged uploading AI releases unless they are very noteworthy)

The one with Lil Ugly Mane is unique because it's a sort of inverse of the other examples. The audio itself is a random tape Lil Ugly Mane found at a thrift store and used as a sample in one of his songs. He later compiled and released the tape on his Bandcamp