I wouldn't trust "commit counts." The quality and content of a "commit" can vary widely between developers. I have one guy on my team who commits only working code that has been thoroughly tested locally, another guy who commits one line changes that often don't work, only to be followed by fixes, and more fixes. His "commits" have about 1/100th of the value of the first guy.
The author does not look at counter values but rather at how the values changes. That reveals dynamics.