Version is 1.20.1. There isn't really much to say. I think tomes from Quark don't care about how many items are in the first slot and allows enchanting more than 1 item at once. The image shows annihilation planes from AE2 all enchanted with fortune 3 getting enchanted by fortune 4 with a single tome. And yes, annihilation planes can be stacked, even if they are enchanted. AE2 developers prevented regular book enchanting to work with more than 1 plane in the first slot.

A single plane getting enchanted with fortune 3:

More than a single plane getting enchanted with fortune 3:

This method is overpowered and I assume not intended at all.