How dam confusing could he have made it. The description of two weapon fighting clearly states compare the difficulty of the two weapons being used. He does seem to be contradicting the rules in his statement. It is possible that he is talking purely about setback and boost dice. I wonder what he would say about using weapons with cumbersome or unwieldy as these are the only other ways for a weapon to increase the difficulty of a check. Let's hope he comes back and answers the questions others have put to him. I can see where the qualities of one should not affect the dice pool of the other weapon, but surely you should be looking at the entire dice pool of each weapon and choosing the one that is most difficult then applying the boost/setback for that weapon to the pool.
Fingers crossed for an answer