I often suspect that Google's extreme secrecy about the internals of their search engine algorithm is less about keeping people from "gaming the system" and more about hiding just how simple minded and arbitrary it is.
I am still writing "dirty code" but when I had started with programming it was looking even worse and I have never been able to understand "what, the hell, I've been thinking"
Maybe in Google's case it's the same? Maybe it's not simple code but very, very ugly one? They might think: "Why I put THAT? What does it suppose to do? Why? What? How? ... OK. It is still working so I will not touch that!"