It's really not. It has the same flaws, some libraries that promise to avoid them (as long as you don't hold them wrong - what every single programmer does), and lots and lots of new flaws that may come from anywhere.
That depends on how you decide which bucket something gets thrown into.
The C++ community values things like the RAII and other features that developers can use to prevent classes of bugs. When that is you yard-stick, then C and C++ are not in one bucket.
These papers are about memory safety guarantees and not much else. C and C++ are firmly in the same bucket according to this metric. So they get grouped together in these papers.