toString is only used to parse the function signature to get the list of dependencies. If you use the other syntax it doesn't have to do the "magic" at all. I haven't looked at the output (though the magic function itself is pretty simple) but I would imagine it just creates the explicit version that you can choose to write manually.
I'm a little torn myself; on the one hand, I prefer explicit code without magic. Having said that, you often need quite a few dependencies and it's a pain, and ugly, to write them all out twice on all your signatures.
