Maybe he's saying that he wants us to play the forwards that we've got, but if we find a useful center or backup PG/combo guard on the grad transfer market, that might make sense.
He is NOT saying that. Here's what he said:
"we've progressed past the point of needing guys who can't crack the rotation at Wake Forrest.". As you can see, his statement applies to any position.
With respect to your point, first do some research on who is actually available. You will notice that grad transfers from power conferences are few and far between. And of course the stronger candidates are likely to have plenty of suitors. Some may also not be admissible to NU for academic reasons. Hence, the coaching staff may just have to settle for the stronger that is actually available to them, even if his position is non-ideal. Furthermore, considering injuries, the deeper positions now may suddenly become thin later. So, who can really predict the team's needs, say, half way into next B1G season??