The < Back_to_previous_app is too small. It was clearly shoved into the OS long after the overall design was set. I feel it's correct that it doesn't take over the regular swipe-right-to-go-back navigation. Doing this better would have forced a significant redesign of the fundamental UI paradigms, IMO. That could have been very interesting.
I have not tried Android's event history thing. Whenever anyone hands me an Android to show me something, as soon as I hold it I manage to activate some "home" or "back" or "change app" feature that takes me away from the thing the other person was trying to show me. I've no idea what control I'm accidentally tapping, just by holding the device, but it's pretty consistent. So I'm not yet convinced of Android's improvements over iOS.