Found a typo as I was implementing this. On the slider dots implementation page, under the “Active class” dropdown, the documentation says to add the attribute to the “content” element.
Well, I did that, and it didn’t work. The sentence right before it also says to add to the “Slider” element. I then added the attribute to the “Slider” element and confirmed that adding the fs-sliderdots-active attribute to the “Slider” element is in fact the correct way to do it!