I does do what it says.

At first I thought Ghost Dog was right in that it doesn't add more than 2-4 harmonics but when I tested it thoroughly with a sine wave it showed a lot more.

Test scenario was melda sine wave generator, voxengo span pro, cubase 9.5, win10 pro. - I have to say though that you need to send quite a volume into it (!) otherwise it just produces the 2-4 harmonics.

So just 4 stars from me. The volume thing could have been described somewhere.