Earlier quoted context omitted.
At the very beginning of this excellent interview https://www.youtube.com/watch?v=sfXn_ecH5Rw that I found in the comments here, they explain this. Apparently, for this to work, they have to "affix them to a physical medium". Strongly recommend watching that video! Excellent info.
Hm, they don't really explain this, or do they? They just say "by saving those melodies to a hard drive they have affixed them to a physical medium which is all that is necessary to copyright them". So, by the same argument, they could copy the self-extracting archive to a hard drive, and then have the same thing, or not? They even say that they already store it in a compressed form on the hard drive. What if some fu…
“But are the tunes really affixed to the medium?”
“Yes, this hard drive in my hand literally contains a bunch of MP3 files” is a lot stronger than: “Yes, in a way, because this tune-generating script technically constitutes a self-extracting archive, your honour.”