Delete "@IBOutlet ... NSWindow"

In chapter 1, under the “Showing the Window” section, the instructions directs one to delete “@IBOutlet weak var window: NSWindow!”, to be replaced by (Swift) code that instantiates the controller, window, etc.

Is this done to make clear to readers the code that would be generated by the IBOutlet method (behind the scenes), or is the behavior actually going to be different between the two approaches?