I don't really agree that the home button behavior is confusing. The home button complements the back button to give you two options: stay in the app or go back

I don't really agree that the home button behavior is confusing. The home button complements the back button to give you two options: stay in the app or go back to where ever you came from. I think the more real problem is that developers have been really bad at choosing the right default behavior for things like launching from notifications, widgets, or intents. These things are often the most likely way someone will interact with your app, so implementing them needs careful attention. At a minimum, an app like Gmail should offer a configuration to change the behavior even if they want to choose a weird default that overrides standard system behavior.