and the mk-339, which your quoting from, has a pilot option funtion, which allows the pilot to choose between two settings, depending on which bomb rack arming solenoids he selects to arm(these retain the arming wire if selected; which pulls it out of the fuze as it drops). what's being said about the 339 is that the pilot must either select nose, or nose/tail. if he selects the tail solenoid only, the fuze duds. but again, the 339 would NOT be used on anything else but a cluster bomb.
from the article: Report: UN evidence counters Israel's account of Gaza war