Yes, this is a documentation bug. If you look at the actual Makefile in the layout, $InstallationDirectory/SystemFiles/Links/WSTP/DeveloperKit/MacOSX-x86-64/WSTPExamples/Makefile, it is correct.
The difference between the libraries in CompilerAdditions and the ones in AlternativeLibraries is the usage of the libstdc++ runtime vs libc++. Since Apple changed the default in recent versions of OS X/Xcode, one should either add the -stdlib=libstdc++ flag with the first set of libraries, or else use the alternative set.
