My guess is they are looking for affirmation that you have agile experience. One of the tenets of agile is having a well-groomed backlog and that means, absolutely, that the stories are rank-ordered. The benefit to the team is clear direction on what to work on next. A program manager acts as a hub to get confirmation from all stakeholders and maintains the backlog in a system like Jira so the next sprint picks up the next highest ranked feature. And--surprise--priorities change so what was number 10 last week could become #1. So your answer should indicate how you communicate with the stakeholders and ensure current priorities.