Oh, we know for sure that it is reposting partially disguised sentences written by a human author. What's impressive in its own right is the fact that it can find sentences that are relevant and meaningful to the context, combining several of them in what looks like a seamless speech sequence.
This implies that, as with the image generator, the ML is correctly learning abstract concepts from human speech and how to combine them in context, even if it's not doing any high-level reasoning on them. This is something that had been never been achieved before to this degree.
