Curtain walls are flexible and powerful. Part of that flexibility and power comes from the way you can set up a curtain wall Type with grid setting-out, mullion and panel types, but then override those defaults individually: You can unpin just one panel to change it into a door, for example.
Contrast curtain walls’ flexibility with that of railings. With railings, you can set the spacing of the balusters in the Type, but there’s no way to override an individual baluster in a particular railing instance.
Default + Overrides. It’s a powerful, flexible pattern.