That makes no sense. First, even if that were a general trend, PBPL breaks it. As you would expect from a department whose members all have PhDs in economics or political science, it’s just a mix of economics and political science, two fields which are not generally considered to be preprofessional. Second, the trend you posit does not exist, at least at Chicago. Cinema and Media Studies at Chicago is nothing like actual preprofessional film departments like USC SCA, for example, but a mix of art history and English with a focus on film.