1. Add a folder into Document and Media.
2. Drag a "Document and Media Display" portlet to page.
3. Click on the folder and assert that you can see its contents.
4. Enable page customizations for the column which "Document and Media Display" just locates to.
5. Click on the folder again and assert that you don't see its contents: the portlet behaves as if you hadn't navigated to the folder.
This can be reproduced with an Asset Publisher portlet too. For step 5, just click on any listed asset and check how it does not navigate to the asset detail.