Katniss can see that the other competitors are purposefully keeping Peeta alive, but she’s not insightful enough to see the bigger picture, and comprehend why they would do such a thing. There seems to be no reason to save Peeta, at least not within the limits of the rules of the Hunger Games. This suggests that Johanna and Finnick, like Katniss in a sense, are thinking “outside” the Games to bigger, and more mysterious, things.