Although it inherits from C several kinds of user defined type, C++ chooses to neuter all of them so that in practice any real user defined type "is a class". One of the many cringey Herb Sutter (IIRC) stunts at CppCon was singing "all you need is class" to the tune of the Beatles' "All you need is love".

But crucially here what we're talking about is the choice to define the concrete data structure inline with the definition of a class as "member variables" and to also mix in these "member functions" which aren't part of that data structure. That's an unnecessarily confusing way to do this.

Unlike "member function", your "code module" is not in fact part of C++ nomenclature. You're of course welcome to invent your own terminology to explain what's going on but it does obviously undercut the claim that this is "clean and readable" if you had to invent your own terms to even talk about it.

I do agree with you that writing C++ is a bad idea.