The significance of this quote is that when Pi Patel meets the second castaway, he is also a Frenchman. Therefore, the two Japanese men (grasping at straws), seem to think the other castaway must be the cook from the ship.
Pi gets more and more frustrated as he shares his story with the two Japanese men from the Maritime Department. Considering they have traveled a long way simply to find out what really happened to the ship, the men will grasp at any small similarity in order to create a connection that isn't there.
In the grand scheme of things, these correlations are insignificant. Still they grasp at straws:
"Maybe the Frenchman you met was the cook."
"Maybe. How should I know? I never saw him. I was blind. Then Richard Parker ate him alive."
Interesting to note here that the concern of the Japanese men is the legitimacy of the story and the convenience of the Frenchman disappearing in order to hide what they think is the truth. Further, the concern of Pi Patel is the fact that Richard Parker ate the Frenchman alive which "was horrific and it stank." It's always good to focus on what is most important, I suppose.