Discrepancy between CMake toolchain file and emcmake

Why is the `--experimental-wasm-threads` argument only set in emcmake and not in Emscripten.cmake?

https://github.com/emscripten-core/emscripten/blob/7df40381247896886e918b5e7086ec7fe6df3e5b/emcmake.py#L41 vs https://github.com/emscripten-core/emscripten/blob/7df40381247896886e918b5e7086ec7fe6df3e5b/cmake/Modules/Platform/Emscripten.cmake#L411

If it was set in the latter, it would make using emcmake and using just the toolchain file more equivalent.
One usecase for this is VSCode based development, where the editor's CMake plugin runs the CMake 'configure' step automatically whenever CMake files change. A so called "kit" file ([link](https://vector-of-bool.github.io/docs/vscode-cmake-tools/kits.html)) can specify a toolchain file, but not a wrapper executable.