I have seen to the first image before and have always liked it. The key to that image for me is the blurring of the arms in movment and the graphic of paint(?) and the open pipe/conduit above his head. That part of the image looks like a pair of wings or an abstract bird. It is a compelling combination of something static and something moving. That graphic element I think lets the viewer subconsciously project the idea of flying onto the boy. Also gives me a feeling of simple joy and whimsy in play.
Perhaps Meatyard saw the samething in the wall and asked the boy to wave his arms. Still makes it a good photograph.