Perhaps the spokescritters-that-be have been sternly told not to divulge anything that might reveal how much we know about those networks. That seems the nicer hypothesis. Maybe it's true.
Alternatively, they may be trying hard to keep Americans from blaming Muslims in general for the incidents of fourth generation warfare. If so, I believe they are mistaken.
If the terrorists are guided by a network, the network can be tracked, understood, and selectively attacked. Lone wolves who spontaneously decide to become enemies can't be tracked. Dealing with them involves much less selective means.
A network is separable from the Muslim community: Muslim with associations = enemy, Muslim without = ordinary. If the model is "spontaneous conversion to enemy," this changes the mapping: Muslim=x% chance of being an enemy simply because he/she is Muslim. Maybe that's actually true, but there are some hints that it isn't.
If the folks in charge want Americans to not blame Muslims, I think they should steer away from the lone wolf narrative, and concentrate on the associations. (Unless they're trying to hide how much we do know.)