Steps to reproduce:

1. Open a world with cheats enabled in 1.21.4
2. Run the command

   /give @s minecraft:written_book[minecraft:written_book_content={title:"TITLE",author:"AUTHOR"},minecraft:hide_additional_tooltip={}]

3. Observe the tooltip
4. Close the world and reopen it in 25w02a
5. Observe the tooltip of the previously given item, or give it again and observe the tooltip

Observed Result:

The author and generation is not shown on the book in 1.21.4, but is shown in 25w02a

Expected Result:

The author and generation are hidden in both versions.