The motivation for the current behavior is: If you switch to
overview mode, you probably want to see as much of the file as
possible, so my instinct was to put it back to the first heading.
But maybe you are right that this is not good if there are many
screens full of top level headings......
It is also INCONVENIENT when each top level has a lot of level 2
entries. For example when you are looking at a subtree and suddenly
want to see an overview of the document, you often want to get back
to the original subtree after visibility cycling.