How is Navigation Drawer different from Tabs, for "back" navigation?

Question

The app is similar to the one described here - one Activity, several sections accessible from Nav menu toggled by always-visible hamburger or by sliding from left edge.
The sections are very different - say, one showing a list, another: settings, help, logs, etc.

Google's guidelines (here and here) don't seem to provide tips for this exact case, thought frequently I find the interpretation that the back key should switch between the sections.

This is not something I'd expect to happen if we had tabs, and I've thought of the nav drawer to be an equivalent. Is it not so, and if not, what's the justification?

Answer 1

Nick Butcher, a Google Design/Development Advocate, has addressed this in this presentation: https://plus.google.com/u/0/photos/+NickButcher/albums/5981768132040708401/5981768199164803938?pid=5981768199164803938&oid=118292708268361843293 : "Selecting a section in the drawer should reset your task back stack".

Also, the reason why the back button does not switch between tabs is because Android's tabs are swipable and appear to be part of a single screen. (Sometimes, the tabs are below the action bar, which may stay the same for all sections.) If you swiped from the first tab to the third tab, then back to the first, it would be silly and exhausting for the back button to take you to tab 2, then 3, then 2, then 1, especially since you never really intended to look at tab 2.

Navigation drawer sections, on the other hand, are clearly distinct screens and the user visits each one intentionally. That's why some apps add these screens to the back stack.