Lots of wild guesses about mixed human-AI copyright in here. Last time I read the copyright office’s statements in this, their stance was basically: The human owns exactly what they contribute. The rest is public domain.

Yes, that is vague. I think the examples were like:

If you paint a symbol and use an AI filter over that to stylize it, you own the symbol aspect of the image but not the stylized final result.

You can own a book of AI images as a curated collection. But, not the individual images.