Enchanted books does not have a stacking limit

How to reproduce

1. Open a world in creative mode and place a chiseled bookshelf
2. Fill out all the slots with enchanted books
3. Keep adding enchanted books to the bookshelf
4. Notice that the enchanted book in the inventory is stackable. Its number increases each time when putting another enchantment book into the bookshelf, without an upper limit

Please refer to the attached screenshot