I have found conflicting information on the availability of NSAttributedString for iOS versions before 6. It is something that would be really useful if it is somewhat back
https://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSAttributedString_Class/Reference/Reference.html
In iOS 6 and later you can use attributed strings to display formatted text in text views, text fields, and some other controls
It is only IOS6 afaik. The class was available prior to IOS6, but the functaionality was not available. So your final assumption is correct :)