The majority of that C and C++ code is hand-written, and not just the output of a compiler or an assembler. They have directly been used to craft some of the most important, and often most difficult to implement, parts of the web application stack.
It's absurd to claim that C and C++ aren't suitable for web development when a huge part of basically every web app today is written in one or both of them. They aren't just suitable for web development; they are critical for it.
You're arguing semantics so let me continue the pattern.
In any non-trivial (jobs/money are on the line), web development != web programming. C/C++ is suitable for web programming, sure, but web DEVELOPMENT is an entirely different matter and is highly dependent on the availability of support, both community and professional, staff, and the competency threshold (or "learning curve") which is the knowledge you need to contribute meaningfully. The latter is one of the most important, especially since the vast majority of C/C++ programmers are not web developers, and doing something wrong in C++ is a lot easier than in memory managed, interpreted languages.
It's absurd to claim that C and C++ aren't suitable for web development when a huge part of basically every web app today is written in one or both of them. They aren't just suitable for web development; they are critical for it.