I'm not smart enough to understand the math in the paper, but I'm able to see that the illustrations match the minifig hand example. This snap fit is present in a lot of LEGO pieces. I'm sitting next to SF, Shanghai, and Kyoto architecture sets, and the 3-in-1 deep sea creatures set, all of which use different snap fit pieces. However, I can understand the confusion given most people's first image of a LEGO piece.