The Facebook targeting functionality consists of two pages: The targeting page and the Targeting interest results page.
With this targeting page, you can connect your own ad account, select your interests and copy them to your adset with a button click. That means you can select for instance 30 interests. With the special ad view functionality on the interest results page, you can then see per interest the conversion, the cost per click and so on. You can then continue with the interests that have the highest conversion, and remove the interests that have a low conversion or are expensive. In businessmanager this is not possible. To know what interest has the highest conversion you have to create a lot of ads and that would mean a lot of costs. So with the functionality, you can find untapped interest groups and save a lot of money!