I think his point has been closer to what everyone else's has been: You can't predict how someone is going to pitch the following year. Koji could be lights out in the closer role again or he could get injured, or suck it up so bad they have to stick him in garbage time innings...
Just look at guys like Jordan Walden, dude was insane in 2011.. Have you heard his name much since? I haven't. Take a look at Fernando Rodney, he was virtually unhittable last year, now he's pretty much an average reliever.
They're just saying go with the live arm, if Koji is still pitching like he is, by all means stay with him. If he's not, give someone else a shot.