1.16.5, 21w11a, 21w13a, 21w14a, 21w15a, 21w16a, 1.17.1, 21w38a, 1.19.2
Both knowledge books are used when holding one in each hand.
1) Get 2 knowledge books
2) Put one in your main hand and another one in off hand
3) Right click
4) Notice how both get consumed, only the one in the main hand should have been consumed
The expected behavior would be that both knowledge books are not used when holding one in each hand. Only the one held in the main hand should be used.