it's possible that the way the menu options for medium type is presented (main medium types followed by specific sub-types indented) may mislead some editors into thinking the main types are not selectable (or not supposed to be used), and they pick one of the sub-types instead, sometimes erroneously (eg, CD-R when it should be just CD). one solution perhaps is to repeat the main type as one of the sub-types, and make the main type grayed out or not selectable (though it's not too elegant)