The pzCreateCase activity can be used to create a top level case or child cases. In your screen shot, I see you are creating subcases. So, in your case, pzCreateCase will then call the pxAddChildWork activity, which is where you will see the PageProperty being used.
Here is the information from the pxAddChildWork description:
"If PageProperty contains a pagelist or pagegroup, the activity creates a work object for each entry. If PageProperty contains an embedded page or is blank, a single child object is created."