We don't doubt that complexity evolved. The question is what were the processes? It stands to reason there were processes, but the process could not be natural selection. The U. Mich lessons say nothing unscientific. But the Berkeley lesson says natural selection explains the complexity of life. Likewise Gerhart and Kirsner and Kenneth Miller do not say natural selection explains the complexity of life, but Richard Dawkins does.
Who cares what someone says in some book you have managed to dig up? What counts is what is.
In any case, you are ignoring the ratcheting effect of natural selection. The important point is that helpful variations are sometimes retained. Sometimes these useful variations are more complex, sometimes not. Once retained, complexity can be increased by further rounds of the same effect.
What is so hard about all this? It's a very simple algorithm that anyone should be able to grasp easily. It does not even need to instantiated in biological systems but can happen in other contexts, such as , for example, computer programs or cultural artifacts. Anytime variation is coupled with selection, evolution happens.