I'm not sure. In the new iTunes, almost all on-screen elements are now actionable, but only some of them have traditional visual indicators like button outlines or pop-up menu arrows. (For example, a playlist can be renamed by clicking on the large title which looks just like a static header.)

The new iTunes UI doesn't have any mouse-hover effects either, apart from those that are part of the OS X standard window decorations. This suggests that the new UI is designed primarily for touch rather than mouse use.