Uh, he's saying it because the kid is overly confident and acting as if he knows Williams' life because he saw a painting and drew a bunch of conclusions, so he was providing a life lesson to realize that experience provides a level of understanding that book knowledge will never be able to capture. And then he even re-affirms this to Will and emphasizes that he can't possibly know what makes him tick because he read Oliver Twist. Your tangent seems entirely unrelated, IMO.