It's all about the person's experience and their perception of the experience. There can be many different sides to a story and it most likely represents the truth of each individual. Tim O'Brien is a perfect example, he explains his truth about the Vietnam War in his own way and how he felt through his experiences. You get to see Tim O'Brien explain his personal truths, and while he may have had different ways of explaining the Vietnam War, it's his truth. Whether it was Jimmy Cross and his love for Martha, or the horrific experience of killing Ted Lavender. He did a great job telling the story, whether it metaphorically meant something else or was a figment of his imagination. It was his truth about Vietnam