I'm confused with understanding Xcode 6.1 simulator versus assistant editor

I created my game apps in Xcode 5.1.1. Yesterday i downloaded Xcode 6.1. I downloaded 6.1 because i also want to make my app on iPhone 6 and 6+. Why is it when i upload the simulator for all iOS 8 devices the simulator loads normally full screen as if i already made adjustments for the phone for it's 4.7inch and 5.5 inch when i haven't. However, in assistant editor storyboard preview under the 4.7 inch and 5.5 inch phones there is a HUGE empty space because i haven't yet started fitting my 4 inch game designs for iPhone 6. So since simulator already loads the iPhone 6 design perfectly does it mean i don't have to actually custom build a 4.7 inch and 5.5 inch screen?? I'm confused.