Why are MKPolyline and MKPolygon working in iOS 3.2.2 (on an iPad)?

As far as I can tell, technically MKPolyline and MKPolygon should not be functional/available when running on an iPad or any other device prior to iOS4. Nevertheless, when I installed 3.2.2, on the device, and updated my build tools with the la开发者_如何学Pythontest (non-beta) iOS 4.2 SDK, they both work just fine, along with their associated views. What the hell?

I'm not exactly complaining here, given that the alternative would be NVPolyline and it doesn't play well with a huge number of points. I'm just confused. Can someone explain why these classes are available and working on the iPad?

I have not, however, had any success subclassing MKOverlayPathView on 3.2.2, even though MKPolylineView and MKPolygonView both descend from it.

The docs certainly claim that it was first available in 4.0, but I remember the new MapKit overhaul being part of the diff for 3.2. I think the docs just have the timeline of that update wrong.