Right now, the UI kit only contains the newest changes in iOS 10— because we're assuming that designers already have copies of their own iOS 9 UI kits and can be redundant to copy it all over.

Maybe, once the golden master version of iOS 10 is up, we'll have a fully-fleshed out UI kit that includes the standard navbars, segmented controls, sliders, etc. — plus Sketch files for every stock app available.