You can't overstate the importance of a specification. It is the most loathed thing to write, like unit tests, but in the end is essential. I think the OP romanticizes a bit: K&R C had a spec, a very very very loose spec. It took ANSI a decade to put some meat on it. Early C compilers weren't much help: Sparc had SystemV and AIX had POSIX which are OS specs but still defined C behavior in their compilers, and it made life so much easier in the early 90's when they converged on Gnu.

My favorite part of the article is the footnote. We really need to stop referring to C/C++ as "roughly the same" because they are so so so radically different.