The Jhanic Zen meditations even at their deepest level both the material and immaterial jhanas were not enough for the Buddha. The Buddha's enlightenment came from taking a further. We find these teachings in the Pali texts. Are such texts not more useful than studying koans?

It is good to know about how the Buddha trained. But there is nothing to study about Koans. It is not about knowledge. The Koans are alive, asking you, who are you? They make us touch our life energy. Any kind of understanding would be standing in our way. If you do not throw away all knowledge, your life will turn into mere knowledge. So it is actually not important what kind of training the Buddha did, only the experience of the Buddha is what matters. The Buddha realized human´s pure mind beyond any study or knowledge.