Remember we now KNOW for sure that the sub imploded, given the debris field, which means a sound loud enough to be picked up was generated. The Navy staying schtum on this does no one any good. It's also possible that someone in the political leadership overrode the preferences of people concerned about intelligence, but in this case I suspect that it's just pointless to deny it, so why not leak it now when it's going to be swamped by the news cycle.