quilletteThrow

The paper doesn't have a conclusion, really. It describes a model and is supposedly intended to spur greater discussion. This is probably part of the reason the paper is written as it is: meant to be simple and easily accessible to people in other fields. The parent will need to work harder to dismiss the author...

There are different notions of variability used in the paper, and he is showing one is equivalent to the other. It doesn't seem ridiculous to me to include the proof, even though it is simple. Lots of simple proofs are included in papers and books.