Grindstone can make 2 books in one slot

If you put a book with enchantment Curse of binding in the Grindstone slot, and then put a book with the same enchantment in another slot, then instead of issuing a regular book and experience, books with the same enchantment will be 2, but you can't put a book with enchantment on a slot with the same book, and this works with a book on enchantment Curse of binding, I'm not sure if this bug works with other books curse, but this bug just breaks my brain, if you don't understand anything, then watch two comparison videos, where does version 1.16.3 and version 1.16.4 pre-release 1 compare. I hope you understand me, have a nice day!