In a recent presentation from a Google employee (Navigation anti-patterns), it states pretty directly that it's bad practice to navigate tabs using the back button (see this slide - https://plus.google.com/u/0/photos/+NickButcher/albums/5981768132040708401/5981768188790396002?pid=5981768188790396002&oid=118292708268361843293)
I agree with this, however in a significant number of user tests being run, users are hitting the back button in certain instances expecting it to go back to the first tab. They're getting (audibly) frustrated.
As an Android dev, going against Google's guidelines irks me, but at the same time, the problem is there (with a potential fix). Should I stick to Google's guidelines? Does anyone have experience with this? Is there something else foundationally wrong with my navigation if users are expecting back to go to the first tab?