Not sure what is meant by this statement. Both cpp2 and Carbon are different languages, neither of them claim to be just C++.
Both languages will have bidirectional compatibility with C++ so that code written in C++ can be directly accessed from Carbon and code written in Carbon can be directly accessed from C++. Neither of them use an FFI for compatibility.
Both languages will have bidirectional compatibility with C++ so that code written in C++ can be directly accessed from Carbon and code written in Carbon can be directly accessed from C++. Neither of them use an FFI for compatibility.