The audio directly in the post was for sure, but did you listen to the audio in the linked twitter thread? The only thing that gave me pause was the gpt text itself not the voice audio.
I had not listened to the audio in the twitter thread. It's a lot better and the only issue I notice is the pauses at the end of sentences don't seem quite right. I don't know if I'd notice the pauses though if I were not going into this with a suspicious mindset. After listening to the twitter thread I'm not convinced I could detect the difference if it was two random clips one generated and one not.
The Twitter audio had a distinct "key note address" cadence to me rather than being conversational. Of course probably most training voice came from such addresses.