You miss my point in disabling the back button. The user still needs to test it every time to see what it does and where it goes, if it works at all. That's bad UI.
As for going back to the previous app, as I argue below, the back button is crippled there too because you need to be in the root view controller of whatever stack you're in for it to do that, and you need to remember which app sent you there, which is not indicated in the UI.
In iOS you can get back to the previous app from anywhere in the navigation stack with a double-tap gesture. An additional tap, to be sure, but all ambiguity from the constant and ever-present back button is removed.
It's bad UI if the developer programs bad UI. The back button returns you to the previous activity by default, you can override it but you should have a good reason. If I downloaded shovelware from the app store and a button labeled 'Play Game' actually took my photo and uploaded it to hotornot, I wouldn't blame iOS for allowing buttons to do things other than what they said.
That's also another thing: iOS is app-based, Android is activity based. You don't have the same navigation possibilities in iOS so you can get by without it. When you flow from one activity to another, you want to return to the previous activity rather than the previous app. Hence the back button.
I talked about UI indications for the previous app elsewhere, but it's dishonest to present the lack of indication as a point against Android when iOS doesn't even have a precise analogue of this, and what feature it does have already exists Android by long-pressing Home!
> but it's dishonest to present the lack of indication as a point against Android when iOS doesn't even have a precise analogue of this
No it isn't. This whole argument just boils down to whether it makes sense to require an unlabeled backward pointing arrow to be present at all times in all UIs. In practice it doesn't make much sense to require a button that isn't always used and doesn't always do the same thing just for the sake of returning to the previous app from an empty navigation stack when you need to do that occasionally. iOS might not do it, but this comes with the added benefits that no back buttons anywhere in the iOS UI is ambiguous.
As for going back to the previous app, as I argue below, the back button is crippled there too because you need to be in the root view controller of whatever stack you're in for it to do that, and you need to remember which app sent you there, which is not indicated in the UI.
In iOS you can get back to the previous app from anywhere in the navigation stack with a double-tap gesture. An additional tap, to be sure, but all ambiguity from the constant and ever-present back button is removed.