iOS 13 Books app and parental controls

My daughter is 8. She has been using our old devices practically since she was old enough to hold one: initially an old iPod nano to listen to music and audiobooks, and when she got 6, she got an old iPhone 4 (with no SIM card, and locked down to the basics) that she also used to listen to music and audiobooks that we loaded on it, shoot photos and video and iChat with a very limited number of contacts.

This year's Christmas present will be an iPad so she can finally use some new apps that need an up to date iOS. She is very creative, she likes making and editing videos, drawing, retouching photos, creating music, etc. and her iPhone 4 was not up to the job any more.

I decided to setup the iPad before we give it to her, so it would be ready for use the moment she turned it on. I loaded it with all her content (photos, music, audiobooks), added/removed apps, and then went on to configure parental controls.

Apple gives parents a lot of control on what their kids iOS devices can do and have access to. However, I'm stuck with a serious problem: iOS 13's Books app.

Even though (I think) I have configured all parental controls that limit access to content that should not be available to my daughter, I am unable to limit her access to the Apple Bookstore.

As a result, if she clicks on the "Bookstore" or "Audiobooks" tabs, she gets access to every item available there. Yes, she can not download any of them without asking permission. However, she can see the covers (covers like "My sister, the serial killer") and even more important, she can read book previews and listen to audiobook previews from books from authors like Stephen King and Jo Nesbo!

This is not acceptable. She is too young to be exposed to this kind of content. The Music app gives me the option to hide Apple Music, I need a similar option to remove access to the Apple Bookstore.

Am I missing some setting, or is this an iOS 13 failure?

Here is what my daughter has access to on the Apple Bookstore:

This is how her library looks like, after I clicked on a book preview...

These are her Screentime settings.

Note that for Music, I have the option to not show Apple Music, there is no such setting for Apple Bookstore.