This amounts to saying: Some days I eat eggs for breakfast, but other days I eat oatmeal for breakfast, so I am totally inconsistent in what I eat from day to day, therefore it would make no sense to include me on a survey about what people in my country eat.
You do understand that a single data point might be useless, but when combined with thousands or millions of other data points, it becomes useful? What you do on any one project does not matter, but what you do, combined with thousands of other developers, all averaged together, starts to get interesting.
If you honestly believed your own premise, then you would expect all the results to be the same -- there would be no variation between Fortran, Java, Javascript, Clojure or Coffeescript, cause, you know, everybody is different and does different stuff, and its all so crazy, how can anybody make sense of it?
But we can make sense of it. All that is needed is a good understanding of probability and a sufficiently large data set.
Mind you, the article above might be total bunk. There might be lots wrong with the dataset. But its not bunk for the reason you give: " the number of lines I commit changes more depending on my project (is it simple or complex, for work or for fun?) than on my language."