Java has language-level support for concurrency + some special concurrency classes in the JDK library.
C/C++ use a library-only approach. C libraries include pthreads and winthreads. I think these are provided by the OS, because these threads are kernel threads.
Many threaded c++ projects use nothing but these C libraries.
There are also c++ thread libraries, (probably always) based on the underlying C libraries.
* c++11 thread library
* Microsoft Foundation Classes
While the lucky java developer can afford to focus on a single concurrency tool set, the unlucky c++ developer often have to juggle 2 or more.
Therefore, it’s harder to get the “halo” in c++ concurrency interviews