They are a volunteer project, like much of open source. When someone finds time to do it, it will happen. (personally, I can use boost.regex if I need it, the lack of <codecvt> in gcc is more annoying to me)
Overall, it is probably true, although there are a few C++11 features that Microsoft implemented back in VS2010, and gcc still didn't.
GCC is just too old and big and difficult to work on, LLVM/clang++/libc++ had a better idea: start from scratch.