HiRez
macrumors 603
Considering there is much more needed graphics buffer due to the more pixels in the screen, I am not surprised.
It's not "much more". 1.7 million additional pixels (at 1242x2208) over the iPhone 6 takes up an extra 5 MB for a 24-bit buffer, or 0.5% of 1 GB. Even if you triple-buffer the whole screen in software, that's only 15 MB. It's not zero, but let's not pretend like it's doubling the amount of RAM required.