As you build adaptive apps, keep in mind the limitations of size classes: they are generalizations, not specific guides for exact pixel sizes or devices. Never attempt to determine what device your app is running on, or whether it's in a split-screen mode, based on the size classes.
Instead, make high-level layout decisions on size class, and use Auto Layout to change precise view frames. (See also the UIViewController method
viewWillTransition(to:with:) for a more precise notification of how big a controller's view will be after a transition.)