I don't think this is true. The target audience of the ISO standard is the implementers of compilers and other tools around the language. Even the people involved in creating it make that clear by publishing other material like the core guidelines, conference talks, books, online articles, etc., which are targeted to the users of the language.
Core guidelines, conference talks, books, online articles, etc. are not authoritative. If I really want to know if my C code is correct C, I consult the standard. If the standard and an online article disagrees, the article is wrong, definitionally.
Correction: if you want to know if your compiler is correct, you look at the ISO standard. But even as a compiler writer, the ISO standard is not exhaustive. For example the ISO standard doesn't define stuff like include directories, static or dynamic linking, etc.
