"Unlike Thomas Edison's later invention of 1877, the phonograph, the phonautograph created only visual images of the sound and did not have the ability to play back its recordings."

In my mind this seems like the difference between the visual representation of the waveform an audio editor shows vs the literal bits encoding the actual audio.

In practice one can approximate the original sound from the image of the waveform, but in most cases it will likely lack in resolution relative to a medium engineered for playback.