It's not private API, it's undocumented API. There's a difference.
There are a few apps on the App Store that clearly break Apple's rule regarding their private API. I feel like this is a bit unfair because the rest of us play by the rules.
There's the official rules, and then there's the actual rules. The official rules might say "thou shalt not use these APIs", but the actual rules say "thou shalt not use these APIs unless we've looked at what you're doing and we think it's ok".
I'm sure that Apple knows what Google is doing by now, so as far as the actual rules are concerned, Google isn't doing anything wrong.
The petulant tattletale attitude in the Mac community is really obnoxious.
Not unfair. Chances are you could get away with it too.