Maybe it makes sense to introduce a single rounding radius theming option (e.g. roundingRadius) which is used as a default/fallback for rounded rects in GDG:

• Skeleton of loading cell (current value: 3)
• Checkbox (current value: 4)
• Image cell (current value: 4)
• Button cell (current value: configurable, default is 0)
• Tags cell (current value: height / 2)
• Bubble cell (current value: height / 2)
• Drilldown cell (current value: dynamic)