The problem is that the invocation of the flags are somewhat more complicated. It is due to the file system layout that the additional flags are needed (in theory if you symlinked the SDK into the toolchain, the options would disappear, but make some other things more complicated). Furthermore, the examples are cross-platform (that is, they should be usable on Linux, Windows, and macOS). Each platform's toolchain has its own quirks (see Swift Linux layout considerations (aka Linux is difficult, lets go shopping) for a more desirable state).
However, patches to improve the documentation are welcome 