C is simple, but that doesn't mean it's not powerful, and with power comes... yada yada yada. There are many edge cases to be sure, but as a language, its constructs and features are very simple.
A lot of people have said it. They develop a mental model that is a rough approximation of its semantics, see that their mental model is simple and conclude that the semantics itself must also be simple. Then other people write articles like these to remind the first group that their "simple" mental model is not the actual semantics, just an approximation.