Summary:
When a renamed enchanted book is disenchanted in a grindstone, it loses its name.

This bug also existed in Java Edition and was fixed in 1.14.1 Pre-Release 1: MC-148529.

Steps to Reproduce:

1. Rename an enchanted book in an anvil
2. Place the renamed book into a grindstone
3. Disenchant the book
4. Observe the book's name

Observed Results:
The book loses its name.

Expected Results:
The book should retain its name.

Video:
Minecraft 2022-02-08 15-52-04.mp4