Can't remove child's child page from Book.

What are the steps required to reproduce the bug?

- Create a book, add a child page, add a child page to that child page.
- Try to remove child's child page from book (without deleting node).

What behavior were you expecting?

Either:
- On the node edit form, I should be able to select "None" from the "Book outline" >> "Book" dropdown.
- On /admin/content/book/XX I should be able to "edit order and titles" for all listed first level child pages.

What happened instead?

- Can't remove the node from the book outline without either 1) deleting the node or 2) resetting child's child to first level child status...

EDIT: Uhm, you can't remove any existing book node from a book, without deleting the node?

I've got to be missing something major, any pointers on how to remove a child page from a book without deleting the node data?