How toolbox symlinks work
What you're missing is: The application (in your case toolbox) can evaluate how it was called. To make an easy Linux-example: Say you have a script called myscript, and call it with the parameters para1 para2 (i.e. myscript para1 para2), and the script has a line:

echo $0 $1 $1


It would output exactly what you called it: myscript para1 para2. Now make a symlink: ln -s myscript mylink, call mylink para1 para2, and guess what it will "echo": the command line you called. So parsing the command line, based on the symlink your toolbox was called by, it can determine which functionality you were pointing at.