This is a little different, it's emergency requests, not national security related. National security letters they can just call the NSA and ask if they sent a request. Unless someone can hijack the NSA phone line that isn't a problem, what is a problem is when there's thousands of law enforcement agencies and multitudes of phone numbers and email addresses to deal with.This has been a rising trend among all companies. This is not an Apple problem, this is a “the opaque “national security” mechanisms we put in place as a nation has opened up an easy vector of attack” problem.
Basically the over the top secrecy and spying done behind secretive “National Security Letters” (Google it) has left companies with no immediate way to know whether these requests are real or not.