Coursework at the graduate level is not just different classes than the undergraduate. It is not simply more information on a particular topic. It is designed to be a qualitatively different experience. Graduate coursework is more creative. Students create systems that will help them to be a more effective professional.
Graduate coursework is more self-directed.
Graduate coursework is more rigorous. More is expected of the graduate student than of the certificate or undergraduate student. Graduate coursework is more attentive to epistemological issues. Skills of discernment and critical thinking are needed. Graduate coursework is more attentive to research.