Shitty headline. Their concern is that there's no way for a 3rd party app to disable the mic on iPhones. They're not worried about iOS being insecure, just that if someone wanted to use one to record sensitive conversations, there's no way they can stop that happening.
Funnily enough, it's because of Apple's approach to security. There's no API available for 3rd party software to use because if there was, some asshole would find a way to abuse it.