It's not that "mingw" itself goes any specific way at all. Mingw is just the headers and libraries (mostly import libraries). Since forever, you can choose to assemble a full mingw toolchain with either GCC or Clang. You can use Clang+binutils, or GCC+LLD, or whichever combination you like. For c++ library you can use libstdc++ or libc++, for base library you can use libgcc or compiler-rt. Any toolchain vendor can decide to build almost whichever combination of them that they like.
FWIW, within msys2, there are also similarly a couple of different environments, on x86_64. The default environment (mingw64) uses GCC, binutils, libgcc and libstdc++, while they also provide a separate environment (clang64) which uses Clang, LLD, compiler-rt and libc++ as default components - similar to llvm-mingw.
In neither case it was "mingw" which decided to go any specific way at all, it's just that different vendors can set up different toolchains.