How can you dismiss the possibility that they are doing something new? Or, for that matter, how does he know that there haven't been other terrorist strikes in the past that didn't fit his definition? Perhaps they have never claimed credit for some terrorist strikes..........anthrax comes to mind.
Suppose there are two entities at war - a Nation-state, and a group that would like to be treated as a nation-state, but has no borders or capital.
Suppose the group realized it could not fight the Nation-state on conventional grounds, but sought to utilize a weapons bandwidth that was not seen by the Nation-state's defense systems.
Suppose the group studied history and realized that groups enganged in mortal struggle against each other don't usually share tactical information that may be of use to the opponent.
Suppose the group has chosen as its primary weapons delivery system the single warrior charged with creating maximum chaos with the minimum cash expenditure?
Suppose the group has decided it best to leave little if any trace of its activities after leaving the "battlefield"?
Take a look at Washington, and remember we are at war with Al Qa'eda and have been since 8:46 AM on September 11, 2001, and see if that doesn't make sense.