Why do you find it intensely irritating? Google's a massive company that employees all sorts of different professions and types of people. This puzzle isn't targeting you, seems successful to me.
Why do I find it irritating? Because it seems both elitist and adolescent, in a child-like "secret society" sort of way.
That pretty much sums up the people I have met that work in Google engineering. I have only met a few at conferences, but thanks for putting words to the initial feelings I got from them all.