Well.. if you read their pdf (linked at the bottom of the blog post), you see that they literally turn the Fitness Function into a trainer that leads teams to the most proper ways to play (see pg5 Section "4.5 Fitness evaluation").
The first step in the learning process is that the teams should spread out on the field and be relatively evenly distributed.
Second was, move players closer to the ball.
Third, kicking the ball was given value.
Fourth, getting the ball closer to the opponents goal.
Then finally, the most weight was given to scoring goals.
So.. they have a great system here.. but it is mainly suggesting that these fitness guidelines eventually lead to behaviours that we understand as playing good defense or whatever.
To be fair, I'm guessing that maybe Mr. Elmenreich was using the word "trainer" in some literal sense.. They didn't need some trainer for other parts of the system since that was built into the fitness evaluation step.
What I want to know is: Did they put in a penalty for offsides?