I do get the impression that some here have no idea how things work in the world of holding companies and large corporations, especially large privately held corporations that are not driven by stock prices.
Here is a link that describes exactly how complex it all is.
https://www.bookbusinessmag.com/post...ok-publishing/
For all of the big 5, they are a small part of a much larger holding company. Try tracing the ownership of say, Penguin Books.
It's an interesting article, though I would treat the actual numbers used with a lot of skepticism. As he mentions at the start of the article, there are very few numbers actually reported by the companies themselves.