It's all about learning, evolving, and becoming a better modeler.
By pointing out some areas where he could do better, maybe he listens and learns, and his next model comes out even better. Just giving the guy a pat on the back and telling him how fantastic the model is, while ignoring the obvious issues the model has, isn't doing him any favors in the long run.
Of course, it's up to him whether to take any advice offered, or ignore it. That's his call.