I thought it was pretty easy to pick the audio clips with greater variance in pitch and pronunciation. 2-2-2-1 were the human voices.
I do think the difference would become obvious with a paragraph or more of speech, though. It's difficult to judge what the correct intonation should be on these single sentences without context. Ultimately, correct intonation requires a complete understanding of meaning which is still out of reach. An audiobook read by tacotron 2 would still sound strange.
I thought the same thing initially -- I guess it fooled a few of us with that first one!