Flying Yolk - Ground Scrolling

I have been going through the example projects included with Project Tiny and implementing some of the features in my project where they fit. One thing that I used was the implementation for the scrolling ground. SortingGroup component was awesome for helping me sort everything that was a child of my Entity.

However, I noticed when I pause the Flying Yolk demo, the child entities in Ground actually reordered in the hierarchy as they are repositioned by the RepeatingBackgroundSystem. However, for the life of me, I can not find anywhere in the code where this actually happens! Does anyone know how this is being done?