If you read the last 1/4 of the paper, you'll see that Figure 6 is an integral part of the discussion; furthermore, nothing in the discussion is proven rigorous

If you read the last 1/4 of the paper, you'll see that Figure 6 is an integral part of the discussion; furthermore, nothing in the discussion is proven rigorously --- they all appeal to the picture. That is exactly what a proof by picture is.