I think that you are on the right track.
Charles Krauthammer on Inside Washington tonight (I think that they tape Friday) said that he's seen video of Kerry saying that the U.S. did exactly the right thing by using Afghan help at Tora Bora.
It will be devastating to superimpose that on Kerry's current "Bush let Osama escape by outsourcing at Tora Bora."
Krauthammer seemed to be discussing even more pointed Kerry remarks than those quoted by you. Maybe, Kerry made the more pointed remarks on the Senate floor or some other interview around the same time?
Kerry can always claim that his comments were made before OIF, which changed his opinion on Afghanistan.