Current versions of C have some features that are not present in current versions of C++ (e.g. designated initializers).
But that's not the point. C and C++ are in practice used completely differently, so writing C++ using C concepts with some additions rarely happens in the wild.
... except in the firmware space, where important C++ mechanisms (especially RTTI and exceptions) tend to be unavailable, giving rise to a (useful, powerful, fun) hybrid of the two.
But that's not the point. C and C++ are in practice used completely differently, so writing C++ using C concepts with some additions rarely happens in the wild.