We could have gone after the people who actually did 9/11 but that was a bit of a non-starter. Also I think you're equivocating between multiple interpretations of "the terrorists" when most people absolutely wouldn't draw a distinguishing line between, using 9/11 as an example again, the actual hijackers and Osama bin Laden. There's absolutely no question that any time the phrase "the 9/11 terrorists" is used it means both the actual perpetrators and the people who planned and supported the attack.