You have a good point, but I think the author was making the case that a conceptual understanding AND memorization/repetition are required to make the learning

You have a good point, but I think the author was making the case that a conceptual understanding AND memorization/repetition are required to make the learning stick. I don't see a case for not explaining concepts, but a caution to not go too far the other way. And I saw repetition as being more important than memorization. That by repeating the application of your understanding of some concept, as being the key to making it stick.