As others are pointing out, yes, it's reasonable to not publish an API that you've chosen not to invest in supporting forever.
But it still feels like this is wrong even though we know the above. The reason it feels wrong comes back, as it always does, to Apple's walled garden. If we could 'use it at our own risk' as we might with an unpublished Android API or an unpublished Windows API, everyone would be fine with it.
But when 'unpublished API' means 'if you go near it your app is dead' that is a much less reasonable thing.
How that "use at your own risk" is working out for Android is one notable reason why iOS is successful: everyone isn't fine with it - customers don't like getting the fallout of risks developers choose to make with APIs the OS provider won't stand behind. The walled garden approach succeeds for a reason.
But it still feels like this is wrong even though we know the above. The reason it feels wrong comes back, as it always does, to Apple's walled garden. If we could 'use it at our own risk' as we might with an unpublished Android API or an unpublished Windows API, everyone would be fine with it.
But when 'unpublished API' means 'if you go near it your app is dead' that is a much less reasonable thing.