"Stacked stars" appears as one of the types to select the ratings, however, once selected and saved the changes, the change is not kept.
1.- Go to site settings
2.- Go to Social tab
3.- Select "Stacked Stars" from the dropdown of any of the sections
4,. Click Save.
The selected section shows "Stacked Stars" as the rating type
The selection shows the default value (thumbs) as the rating type
See video attached.