It is not absurd. From manager's point of view, when they are deciding to let someone go or promote them, they often need some arguments. And since software is invisible, it is often hard to just say straight away who is over/underperforming and why you think so apart from a "vibe" you are having. Measuring some relevant metrics can strengthen your argument and/or your overview of the situation.

I don't think that the blog makes a compelling argument why measuring productivity is bad per se. It makes a compelling argument that metrics should not be interpreted blindly, but the metrics in this case identified a guy that was doing something unusual, and the managers managed to interpret why this is the case. But if it was an IC that is supposed to deliver, or if you did not want "Tim" to spend his time coaching people, this could still have been valuable info.