The jamb is defined with the Is under jambs feature on the exterior veneer. By marking the feature under the jamb, the exterior veneer element is extended to the window/door space under the jamb element. If it is not marked, it finishes the exterior veneer on the edge of the jamb, surrounding the jamb.
Location of Is Under Jambs Feature
You can access the feature is under jambs from the exterior veneer settings dialog.
When is under jambs not active
When is under jambs active