I guess this was posted as look back to before they were successful? They've launched the Falcon 9 heavy to the ISS now, so no one would consider them not. Maybe all those failures with the F1 light model are part of why the Falcon 9 was designed to and managed to do its job even with one of the engines failing...
They've been launching Falcon 9's to the ISS. So far they haven't flown a Falcon 9 Heavy (which they have actually renamed to "Falcon Heavy", no "9" (maybe because the first stage will actually have 27 merlin engines)).
