Release Outside

I was looking into one of the new features of Flash 11.3 which is the MouseEvent.RELEASE_OUTSIDE event type. Check out this link to see it in action. While I was doing some searching around the net, I happened to see that there exists a Event.MOUSE_LEAVE event type. This must be new right? No, it's been around since Flash Player 9, the beginning of AS 3.0. How could I have missed this?

Well I guess part of it stems from the fact that this is clearly a mouse event that has been put on the Event class rather than the MouseEvent class. That is rather confusing. The MOUSE_LEAVE and RELEASE_OUTSIDE types are very similar in that they get triggered outside of the stage. The major difference being that the mouse is down and then released with the MOUSE_RELASE while the mouse has to be up with the MOUSE_LEAVE. To me it seems like MOUSE_LEAVE is on the wrong event class. It should be on MouseEvent class. Is there a good reason for for MOUSE_LEAVE to be on Event instead of MouseEvent?