Because why exactly would anyone believe the US government after they have invoked the "secret evidence" trope for the billionth time?

They will claim this to get out of some clerical error. They will claim this for anything. It's unverifiable, it's unbelievable, it's a wonder any publication with some journalistic integrity left would read anything into it.

Here is attorney general Holder invoking state secrets to cover up what was eventually revealed as a lowly FBI clerk checking the wrong box:

http://www.wired.com/images_blogs/threatlevel/2014/02/holder...

This wasn't even an important case! Think what these people will do when the stakes are higher.