The Bug
Operator blocks and items were added to the creative inventory though the knowledge book wasn't wasn't added despite being an operator item.
Reproduce
Create a creative mode world
Open the redstone tab
scroll down
Observed Result
The Knowledge Book wasn't present in the tab
Expected Result
The Knowledge Book would be present in the tab
Well, it needs explicit NBT data to function, and that data is recipes to unlock, which is not really a thing that would make sense to have an item for each in the creative inventory.