What is the purpose of Jean's story to Francis? What can we consider it an example of?

There are several instances of repetition, and most are meant to capture the reader's attention in a specific way. One of those appears in Chapter 23 when Jean tells French how he made the decision to leave home. He says he was praying for guidance in a church and he heard the sound of traffic on the Trans-Canada Highway. That sound prompted him to make the decision to leave the brutal situation he was facing at home. It was also the first step toward the happy life he led with French's mother at his side. In the next scene, Jean points out that Minerva is going to be transferred to the Capital by way of the Trans-Canada Highway. The second mention of that highway is meant to remind the reader that this highway led Jean to a better life, which is apparently meant to make the reader think positively about Minerva's future as well. I think that Jean's story is meant to be a metaphor for change and finding ways forward.