Well, it looks to me like the article itself has already reported the determination and the conclusion .
Although Boeing identified the problem in 2006 and initiated a retrofit programme, the FAA AD and acceleration of the replacement effort was made inevitable by "the subsequent discovery of a second broken rod in December".
Boeing says 880 aircraft have been fitted with the "enhanced" rudder system, of which 681 were discovered to have been delivered with "suspect rods".
Someone, someplace is convinced that the continued operation of aircraft with the "enhanced" rudder system that was delivered with the "suspect rods," is not something that must be immediately stopped for safety considerations. I would imagine that's a difficult seat to sit in - it's a good call if nothing happens; but if one breaks and causes another hard-over rudder with resulting injuries or death - that guy would become the goat of the month!