I can't speculate too much but I can imagine aphex releasing a bunch of stuff incognito around the time of a release just for bonus material as he did for Syrobonkers because he has tons of music and he likes to be nice but doesn't want people to think he's too nice, so it's gotta be incognito...
Also I imagine he would enjoy people pulling their hair out trying to figure it out, but who knows. I do think there are people out there who are talented enough to fool people into thinking it's afx.
also I think it's bs these were made in the early 90s, a lot of the percussion are modern styles like the high hats on parking lot, bimbongo and Suzanne