It is not a stretch it is just plain wrong. C++ has good C interoperability (most C is even valid C++) and most compilers that support compiling one also support the other, but I can't take seriously anyone that refers to "C/C++" as one language.
C code will not accept C++. A C compiler will not support C++ (unless it's explicitly designed as a C++ compiler too). A C-only programmer will be as lost on a C++ codebase as on a Rust, Go or Java codebase.