Left panel: Don't auto-collapse top-level headings

What is the design reason for auto-collapsing each top-level heading as you open another one? (My Tasks, Recent, Smart Folders, Projects, Members)

The behavior actually slows down navigation as it requires two clicks to change from, say, a project scope to a smart-folder scope.

If instead they expanded and collapsed only when clicked, you could open the ones relevant to you and freely navigate between them.