I'm not sure about this. Imagine that a whole subtree got inserted. It's true that the root of the new subtree will be handled by the `generateChildEdits()` of its parent. But all the descendants within that new subtree also have to get inserted, so it seems like we have to walk the new subtree too. (I haven't reviewed `generateChildEdits()` in depth, but from my initial inspection it looks like it only handles one level at a time--it doesn't descend into subtrees--which makes sense in general.)