Isn’t it more like an art gallery of prints of paintings? The primary art is the text of the book (like the painting in the gallery), TTS (and printing a copy) are just methods of making the art available.
I think it can be argued that audiobook's add to the art by adding tone and inflection by the reader.
To me, what you're saying is the same as saying the art of a movie is in the script, the video is just the method of making it available. And I don't think that's a valid take
No, that's an incorrect analogy. The script of a movie is an intermediate step in the production process of a movie. It's generally not meant to be seen by any audiences. The script for example doesn't contain any cinematography or any soundtrack or any performances by actors. Meanwhile, a written work is a complete expressive work ready for consumption. It doesn't contain a voice, but that's because the intention is for the reader to interpret the voice into it. A voice actor can do that, but that's just an interpretation of the work. It's not one-to-one, but it's not unlike someone sitting next to you in the theater and telling you what they think a scene means.
So yes, I mostly agree with GP. An audiobook is a different rendering of the same subject. The content is in the text, regardless of whether it's delivered in written or oral form.