Is there a more complete overview of this traffic situation somewhere? I still find the reasoning a bit hard to understand.

I understand that from this road, you can only ever turn right, and can do so at all times, so there's no need for a traffic light, except that it legally needs to have one because other roads at the junction need traffic lights for other reasons.

So what are the other roads here? Clearly it has to be more than just the Ziegelstraße and the Güntzstraße.