Yup, they are prohibiting an overcurrent device in the middle. If such an overcurrent device were to operate, then the output voltage would rise to the input voltage.
Since the current rating of the shunt winding is less than that of the transformer and the series winding, I can see why someone might want to put an overcurrent device in that location. This would be a case of a safety improvement in a component of a system reducing the over-all safety of the system.
-Jon
