It’s not that folders are acting like documents, it’s that documents can act as folders. It’s all virtual.
The only difference is that the is_folder field is set, and that’s only important in drawing the Document Tree (folders get the cute little folder icon). An "empty" document can serve quite nicely as a container; for example I have the following virtual structure set up for an "Our People" section that uses the FAQ snippet:
Our People (folder, published, has some text and the FAQ snippet called twice on it)
-----> Producers (folder, unpublished, empty)
-----> Person One
-----> Person Two
-----> etc etc
-----> Administrators (folder, unpublished, empty)
-----> Admin One
-----> Admin Two
-----> etc etc
Anyway, if you want an empty "folder" to devolve to a child in your site’s menu, it’s easy enough to make a menu snippet to do that. "if (content == ’’) { query for docs with id as parent, and make their id(s) the link(s) instead }, although that would get a little convoluted when looping for multi-level menu.