Allow Unsigned Books and Quills to Stack in Bundles

Why is it not possible to store a Book and Quill in a bundle that already has a Lectern and signed books, unless it’s a signed Book and Quill? It seems that when the Book and Quill is unsigned, it takes up the entire bundle slot, but if it’s signed, you can store up to 16 in a bundle. There’s no logic to that it’s still just a book used for taking notes or writing stories.

I’ve been experimenting with an Oak Shelf holding items, and underneath I have a Lectern with a book. In my setup, the bundle is useful for carrying my signed book, Lectern, and Oak Shelf together. But I can’t store an unsigned Book and Quill in it, even though I can store 16 signed ones. That feels like a flaw, because it makes no sense to block unsigned books but allow signed ones in bulk.