This breakpoint provides an easy way to track view controller deinitialization (deallocation) in UIKit-based applications. This can help finding memory leaks caused by retain cycles preventing view controllers from being deinitialized when dismissed or popped.
From Cédric Luthi's tweet in 2017:
Useful Xcode breakpoint. When you dismiss a controller and you don’t hear the pop sound (or see the log), you probably have a retain cycle.