But the iPhone does seem to lose differentiation. Android apps have recently become well designed using material design, there's an app saturation, and 90% of the time people spend in phones is inside apps anyway,so it's harder to differentiate on the OS.
But the app does not run within isolation, the OS impacts a lot on the app experience. e.g. iOS Share Sheets/Android Intents. How a tweet is shared from the Twitter app is dictated by the OS
Currently it seems that apple is taking the battle to curation. I'm not sure it has the advantage there - but than again, content quality is very subjective and hard to compare,and than it becomes a marketing game - and Apple is much stronger in marketing.