What is taught about Buddha nature in Theravada Buddhism?

Reference: http://www.buddhanet.net/e-learning/snapshot02.htm The very last row talks about Buddha Nature. According to this page, Buddha Nature is not taught in Theravada Buddhism, and to my understanding, Buddha Nature is the potential for a being to become Enlightened. Is there any reason why the potential to become Enlightened isn't taught? It seems - to me - to be common sense that anyone can find their way to become Enlightened. After all, the Buddha is an example of what all beings could become. Is my understanding of Buddha Nature wrong or is there more to this than I'm seeing regarding how Theravada Buddhism incorporates this in their teachings?