Last February a screenshot leaked of an "explicit" category in iTunes Connect. Soon after the screenshot went public, Apple pulled the explicit category from the list. Is this latest placeholder a sign that Apple will be allowing adult apps back in the App Store? Given the mention of the iPad in the second category it doesn't look like these links were simply holdovers from before.
Some users we becoming increasingly frustrated that generic "sexy" apps (think Babes in Bikinis) were making their way into every category. Apple eventually pulled all the apps to the joy of some users and the dismay of others. An opt-in explicit category would allow for people to choose whether they wanted to see the adult-themed apps or not.