Dogen - On Being Enlightened about Delusion
Those who are enlightened about delusion are buddhas.
~Dogen, Shobogenzo, Genjokoan
Apparently, in the Shobogenzo, being "enlightened about delusion," means awakening to the reality of delusion. That is, realizing what delusion truly is.
Perhaps it is like when, for example, a person is shown the cause of a magician’s illusions: mirrors, wires, hidden compartments and so on. The person can then grasp the reality of the illusion. The reality of the illusion, the mirrors, wires, hidden compartments, is existent, and the illusion is a real characteristic of its existence.
Similarly, when you realize the cause of delusion: misperception or partial perception, of true nature, you realize the reality of delusion. The reality of delusion, misperception or partial perception of our own true nature is existent, and delusion is a real characteristic of its existence. Those who are "enlightened about" this, are called "buddhas."
The Flatbed Sutra of Louie Wing