No, he just compared it to an inefficient distribution (a roof with panels on the south and the north side).
As was pointed out in other comments there are 20 cells on the tree and, most probably, 10 cells on each side of the roof. Had he really compared to 20 cells in a flat panel array, he would have found that the tree distribution is less efficient than the flat panel.
By the way, there is an optimum inclination (vertical angle) of a photovoltaic module, which in Europe is between 30 and 50 (depending on the latitude and the height), see this map (pdf, 11 Mb).
I nevertheless admire the idea and the work of the young boy. As an adult I'm sure he would have spotted the error in the result, unlike the jury and the submitter of the story.