Another odd thing I didn't notice. I just stretched my options screen to try to cover the scroll view instead, just to cheat. But the child elements are always on top of it! No matter what depth I give them, they still appear on top of it. So it's not just the colliders, everything about these instantiations is always on the very top...
I'm simply using AddChild to instantiate them as children of the scroll view, and then giving them a localposition offset, nothing fancy. Any thoughts why they always appear on top of everything?