This makes the mapping between iOS & tvOS/watchOS versions more accurate. For example, iOS 9.3 now gets correctly mapped into tvOS 9.2 and not tvOS 9.3.
Before this change, the incorrect mapping could cause excessive or missing warnings for code that specifies availability for iOS, but not for tvOS/watchOS.
rdar://81491680
Can you add an #else test case that shows the old diagnostic saying that it's deprecated in tvOS 9.3?