It wasn’t written by a mechanical process, though. It was ported (translated) from an existing creative work into a new language.
Surely you wouldn’t say a Spanish translation of a Harry Potter work is in the public domain while the original work is under copyright?
I would agree with you but for the author’s attempt to publish it under a new license. I think they can either claim it’s a new work (in which case it’s public domain) or claim it’s a derivative work (in which case I don’t think they can change the license).
I imagine a court would call it a derivative work if tested.