But the "vanishingly few" are often the most significant features of a particular years iOS upgrade, whereas Google's 1st party apps are for the most part decou

But the "vanishingly few" are often the most significant features of a particular years iOS upgrade, whereas Google's 1st party apps are for the most part decoupled with the major differences between 4.X and 2.X being UI. The situation is much more nuanced than you state.