So what would be the advantage of tapping twice?
As the application is only going in background and the already entered values aren't cleared, the button does exactly what the Home-button is doing.
But the Home-button has no message about are you really sure? Than tap again.
So what evil things would happen on the back button, when you need to prevent doing this action accidentally?
It's simply for the following scenario:
1) I'm in a sub menu like: Settings > Advanced Settings > Codecs.
2) I want to go back to the dialer page. To do this i press Back, Back, Back, Back.
3) I've pressed back 1 too many times and instead of ending up in the dialer page, i've ended up in my Android's home page.
With this verification check, this case is prevented from happening. That's the point. That's all.
Keep in mind that this is a very typical feature in many apps to prevent the user from accidentally pressing the "Back" button one too many times and thus accidentally exiting the app.
Now if the user explicitly presses the "Home" button, this is fine, let him to back to his Android's home page. There's no reason to prevent the user from pressing his "Home" button.
I'm not understanding why this is such a big problem for your part though. Nothing's changed other than the need for 1 extra tap of the back button if you really want to exit the button. I see no argument from your behalf on why this shouldn't be the case, only mentions that it's for some reason "Unexpected Behavior".
Again i'll have to suggest the "Ideas" forum for this. See if your idea gains more traction, lets see other people's opinion on whether this is a good or bad idea and why. Right now from the many users using this app, there's only 1 voicing dislike towards this tiny usability feature, i'd like to see more if it's truly as important as you say.