The test doesn't control for all the variables to make the conclusion that verticals are better than grids. The grid elements having borders and shadows may hur

The test doesn't control for all the variables to make the conclusion that verticals are better than grids. The grid elements having borders and shadows may hurt it. Hard to tell but pics in the grid look smaller than in vertical. The spacing between elements in grid is tighter than between elements in vertical. I'd still expect vertical to do better even if the grid was equally well executed, but reality beats expectations.