He's right, canonically, Sylvanas ordered the Wrathgate in secret. I think blizzard here are doing something like those series and movies with CIA operatives and black ops groups.
Basically, if you get caught or you fail, the governement disavows any knowledge of it kinda thinkg. Varimathras is likely going to be portrayed as using the opportunity provided by the chaos to seize control of the undercity and forsaken and carry out his own agendas