Item file gallery formatting in Thanks, Roy

In Thanks, Roy, one of the display options under Configure Theme is this:

Item File Gallery
Check this box if you wish to display your item files as a grid of square thumbnails and icons.

I have this checked but none of the item displays appear as a grid - not browse items or items in a collection. Where does this option have an effect?

It changes the way the files display on an item page - if checked, the files display in thumbnail size in a gallery toward the bottom of the page