Moving the close paren to enclose each app's upstream app arguments would ease this lisper's eyes. It seems like it might get difficult to debug arity count errors if you accidentally indented wrong somewhere in a larger app.
You're right, it certainly could make debugging harder for large apps, but the point is to stop building large apps. Since every app made using (fab) is itself a (fab) app, debugging/testing should take place at the component levels first.