os x LLVM supports c++11/14, why the include directory is still gcc 4.2.1?

On my new macbook pro, after install xcode, I found:

1. Both gcc and clang are linking to LLVM 7.3. I guess gcc is just an alias of clang here, right?

2. As long as gcc supports -std=c++11 and -std=c++14 parameter, why the /usr/include/c++ only has a directory named "4.1.2"? I know gcc 4.1.2 is quite an old version,