The author's point was that memorization is how you pass these silly interviews. There's a wonderful paragraph in Skienna's algorithm book, where he states tha

The author's point was that memorization is how you pass these silly interviews. There's a wonderful paragraph in Skienna's algorithm book, where he states that if you can reduce your problem to a graph problem you should do so, and that you should never invent your own graph algorithm - the standard ones will solve whatever problem you have. Perhaps a bit overstated, but by and large true. There is definitely value in having all of that information at hand so you can fairly quickly perform the mental gymnastics to find a good solution. I think most people complaining about interviews would agree with that. The thing is that so many people don't work in areas where they need at at the front of their brains, but they do work in areas where similar levels of ability are needed. Product design, finding difficult bugs, working with customers, leading teams, and so on. Bad interviews test memorization. I'm doing almost all linear algebra these days. I can talk to you about matrix computations, round off errors of various implementations, and so on. You probably can't. But only because you are not doing it, and I am. I TA'ed a graduate level Algorithms class. At the time I could do whatever graph algorithm you wanted, now I can't because it is not what I work on now and most of the details have fled my brain. Doesn't mean I can't do it, just like you not being able to implement a Cholesky decomposition on a whiteboard means that you couldn't do linear algebra programming if it became your job.