Run attached application.
Click "Hierarchical order" (that is done to see z-order).

Now, try to do the same on linux and windows:
click in stage0 on "none" button.

stage1 appeared. stage1 is a child of stage0 with none type of modality.

Now the difference description:
On windowsOS, if you click somewhere in free space in stage0, it will still be under stage1. But in linux it surface over stage1.