How to change secondary/fallback language on iOS 8?
For the future reference of anyone reaching this page VIA Google, I found an answer to the problem here. Basically, at the upper-right corner of the screen there's an "edit" button that allows you to change the order of or remove languages, but this Edit button looks like it has nothing at all to do with this "preferred languages" setting which is the second in the list on this page.

(because logic)