Slidey-outy drawer thing shows only sub-nav, not entire bar + sub-nav

At /admin the slidey-out thing shows me the full list of options: Dashboard, Content, Structure, etc. All good.

But when clicking on one of these (say, admin/structure), those entries get replaced by only the sub-nav of the menu item, which leads to problems:

The way the prototype works, the word "Structure" would stay there, but a bulleted list would show below it of the sub-nav.