When an API goes public, can an app still get rejected for using it?

A co-worker and I are having a debate about how Apple treats apps that use a formerly private API. Imagine if you will [NSAppleObject someMethod] where someMethod was a private, undocumented method in iOS 7.1, but as of iOS 8.2 it gets made public. The app supports iOS 7.1 up.

I want to check for the availability of someMethod using respondsToSelector and, if available, use it. My co-worker contends that because this method was private in 7.1 and our app supports 7.1, Apple will reject its use, even though the API is now public.

Insofar as anyone can predict what Apple will and will not reject, is my co-worker correct?