The Timeless Way of Building describes a philosophy, not just of building practice but really of how to live a good, fulfilling life. A Pattern Language is an set of examples of how to shape specific parts of your community and home to implement that philosophy.
Following the patterns without understanding the philosophy makes no sense to me because it’s a very opinionated and, in the modern world, quite radical. What if you don’t agree with it? I think many don’t. At least, you want to be able to read them critically.