When I choose 100% scale in iOS Simulator, the resolution of the simulator doesn't match the resolution of the physical device. Here's a screenshot of iPhone 6 Plus being simulated at 100% on my 20 inch ACD (1680x1050), which should have a width of 1080px:
But it doesn't. Does this happen to anyone else?
How can I fix it?
I think your simulator is displaying at 100%.
iPhone 6 Plus renders at 1242 x 2208 pixels. That seems to match your screenshot.
The problem is that the phone itself displays at 87% to fit its 1080 x 1920 display.