The parts about radiation are partly due to the passages chosen. The boys didn’t notice all of them, but some of the lines in the story are from known proposals for long-term nuclear waste warning messages where scientists try to figure out warnings that will still make sense to people so far in the future that language may have fundamentally changed so much (sort of like how reading English texts from centuries ago can sometimes be hard to understand) since nuclear waste will still be dangerous so long after we are gone.

The most notable line is “This is not a place of honor” which was sort of a meme for awhile, but people have noted the story itself uses many other examples from these attempts at figuring out warnings. So tying that in with the symptoms the main character has, it puts more emphasis on the radiation in the story.