Maybe it's supposed to move from A to B, maybe it should do it in under x seconds, maybe it should go via Y, maybe it has to be easily understood by a 6 years old, etc.
But I can't really imagine something that has simplicity as the only requirement ("nothing" is the simplest thing so that requirement would always be met with no action). So as long as the other requirements are met simplicity is usually the nice to have "add-on". And you can have correct and simple, or correct and complex. But correct (does the job) trumps simple. And the world is surrounded by examples that prove this point.
I think the author meant "simple should be part of good design" but couldn't properly convey the message. He focused on making the message simple and ignored the fact that it's not correct.