Why is SD2 not saved in emscripten's include path?

I'm just wondering why SDL1 is saved under standard emscripten path \emsdk-master\upstream\emscripten\system\include but SDL2 during first compilation with USE_SDL=2 under \user\.emscripten_ports\sdl2\SDL2-version_20\include? This also leads to an faulty includepath #include <SDL2/SDL.h> in Visual Studio Code for Intellisense.