Who are you going to blame when applications start breaking because Apple removes or changes the functionality of a
private function? [1] without warning?
When you are writing any software that has a public API you should feel no obligation to change the functionality or completely remove a private method without warning.
[1] I refuse to call it a private API. An API is public documentation of the inputs and expected behavior of a dependency. It should be a completely black box how that functionality is implemented.
