That's why I said "they claim" for the reason. I suspect for 85% of the general public you could photoshop up some credentials that look like Mulder and Scully's off the intro to the X-Files and it would pass just fine. (that's not what they look like, FWIW)
It may just be bureaucratic BS too. I know we are told not to allow photos or copies of out DOD CAC cards to be taken for the same reason, but it's not like a counterfeiter couldn't find one online in two secs. But the rule is there, and I've seen people punished for breaking it.