The iPhone 6 and iPhone 6 Plus are still fresh in consumers' hands, with Google releasing an updated version of Gmail for iOS. The new version of Gmail works better with the higher resolution displays found in the new iPhones.
It's not a massive change, but the increased resolution, especially on the iPhone 6 Plus, is messing up a slew of apps. At least now, Gmail for iOS isn't one of them. The added pixels on screen allow Gmail users to see more messages at once, without losing Gmail features to a lack of pixels like labels and stars.