I guess I should add that maybe it's not as simple as snapping your finger to make a song your own, but most of these people don't even try. I mean, they just go note for note.
The arrangement tweaks for "Imagine" weren't that sophisticated, but he really seem to highlight the beauty of the tune, and being only 16, I'm guessing he didn't have to be a composer to do it.
I read your reposnse about Johns before seeing it, and I was in agreement from note one.