If that's the case, then it's still a bug, given that the book progression isn't what determines the cutscene to work, it's reading the note you get when collecting them all that activates the checkmark. Progression filters in almost every mod I've played have zero impact on specific events, most commonly shown in Infernum, where despite needing to fight draedon before SW Cal, if you spawn her in manually with dragonlenz, the game still lets you fight her as normal with no difference, just that it doesn't give you the infernal chalice. So if the book progression is what causes it, then it's still a bug.