Well in Reunion Kheylar tried to get Worf to take the oath. But Worf refused because he had been discommedated and didn't want his dishonor to pass on to Alexander.
Maybe the growl these words and we're married is the Klingon equivalent of Elvis in Vegas? Or maybe just "the oath" is something you take as the equivalent of an engagement? I dunno. Not like our own wedding customs aren't goofy at times.