If I had to take a guess this is related to books that have illegal PDF(s) in the wild. Paired with Amazon making little to no effort to verify product authenticity.
https://arstechnica.com/information-technology/2019/02/amazo...
https://arstechnica.com/information-technology/2019/02/amazo...
I don't think there's a PDF for that controls textbook anywhere, so clearly the counterfeiter just substituted in a different one...