Karsh shot Pablo Casals from behind and dead center, albeit in portrait orientation. It's quite possibly the best thing he ever shot.
There are problems with these pictures, but centering and from behind ain't it. The first one the kid does not seem engaged, I get no sense of any personality or activity from the kid's posture, and the context is quite confusing. Is that a TV or a Window? It appears to be christmas? Surely there was a shot of the kid opening a package or something?
The second one is quite nice. I get very little sense of personality here, but there is something appealing in the tilt of the head the set of the mouth and the textures. It's not a very flattering photograph, since it does make the forehead look big, but it's got some appeal. Unflattering and since we can't see the eyes we feel no particular connection here, so I don't feel that sense of "understanding the person" that a really good portrait brings (however falsely). I find it a pleasing picture of a person, but not so much a portrait per se.