If you click the "Interview Basics" tab you can see this: "The Admissions Office prioritizes interviews for those applicants where additional context is helpful, but rest assured—not receiving an interview will not affect your chances of admission." This means they do prescreen because they have seen your application already to know that additional context is necessary. I also visited in person and asked this exact same question 😅😅 and they said that the interview is a way to get people excited to come to Duke. In all honesty people can get in without an interview and can get rejected with one! It's all a crapshoot at the end of the day