I'm thinking Comey is blowing smoke for the benefit of likely terrorist.
Any terrorist is not going to buy a $400 (iPhone SE) to $900 (iPhone 6S Plus) phone when their own website recommends using a burner phone for under $50 that is anonymous, uses their recommended Android OS to run their terrorist Apps downloadable from their own Al Qaida and ISIS Terrorist App store, can be cheaply replaced after smashing the old one into smithereens, furnished with minutes by buying a card at every 7-11 of Walmart.