Their story has changed from possibly compromising sources and methods -- which is patently absured given what we know about the modern surveillance state -- to the fact that "they haven't had enough time to review it".
...we have grave concerns about material omissions of fact that fundamentally impact the memo’s accuracy
Given how much we already know about the unlawful actions of the Obama DOJ and FBI, my suggestion is simple. Release the memo and let the leadership in the DOJ and FBI outline any "omissions of fact" that could absolve them of crimes. My guess is that they won't be able to do so.
Devin Nunes, the chairman of the House Permanent Select Committee on Intelligence, was understandably exercised.