"The Things They Carried" - question 2

In "How to Tell a True War Story", Tim O'Brien tells what he says to be true story about how to tell a true war story using his own for examples. The longest war story that he tells is about his friend Rat who wrote a letter to his best friend's sister after he (Curt Lemon) died.  What is the purpose of conveying the idea that Curt Lemon probably thought he was killed by sunshine and not by a booby trap?

A possible answer to this question would be that this idea is a metaphor. Sunlight represents happiness and/or youthful bliss/innocence as a contrast to the darkness and gloom of the war. Rat and Lemon are the only ones who exhibit a youthful demeanor, a carefree outlook on the world that fades for most people with time and exposure to harsh reality. They play chicken with smoke grenades when they break during marches, a reckless but mostly harmless game of displays of masculinity, while everyone else relaxes. They are playing in the gloomy woods where there isn't any sunlight, but as soon as Lemon steps out of the shade of the trees into the sunlight so that he could face the camp, his life violently ends. The patch of sunlight, the only seemingly comfortable place in the area where they are, is in reality the most lethal. The sunlight almost counters its qualities of symbolism by acting as a spotlight to death, a false sense of security or comfort that leads to death.
Tim O'Brien probably speculates that Lemon thought that the sunshine killed him because it is probably true in a metaphorical sense; Lemon and Rat thought of the war as  "a nature walk", and seemed to think that they were untouchable (66). By emphasizing that Lemon thought he was killed by sunshine could also mean that he thought that he was killed by his own confidence or appearance of confidence and carefree attitude. He was killed by his "sunshine", the thing that kept him sane as a nineteen year old fighting in a war millions of miles away. The war was almost a booby trap in itself, with the draft entrapping any able-bodied young man over 18 into the deadly and hated war.  By keeping their carefree and youthful perspectives alive – their “sunshine”, Rat and Lemon kept the darkness and the nightmares of war and death at bay, just as the older men had letters and other articles of home to keep them sane. Just as Jimmy Cross was blinded by his "sunshine" (Martha) and Ted Lavender died; Lemon was blinded by his and it cost him his life.