I think your defining "human" based on norm. I would prefer to define "human" based on a humans ease of use given familiarity with the notation. I prefer this definition because if you use what I take to be your definition you get oddities like Roman Numerals being more human than what we use today. Given this definition I'm not sure you can say he is purely rationalizing his choice, since he gives a clear example of a situation in which he finds that the notation is easier to use.
Base 12 is better than base 10, but that doesn't necessarily mean it's worth the cost of using it in our programs (I realize that people do use other bases in some contexts, but that's actually an example of coding to the computer's standards).
I don't feel strong one way or another on this issue, though I do program in Clojure. If you want infix math in clojure: http://data-sorcery.org/2010/05/14/infix-math/