Clever terrorists can use innovative ways to exploit vulnerabilities. But don't forget that most bombers are not, in fact, clever. Living bomb-makers are usually clever, but the person agreeing to carry it may not be super smart. Even if "all" we do is stop dumb terrorists, we are reducing risk.
Quite astonishing, actually, and something of an admission. As the article says, the entire system is designed to stop stupid terrorists. When it comes to smart terrorists, well, we're on our own.