I'd also guess that you will qualify for the Mile Play promo. I had a situation last year with even less of a "change" that qualified me by surprise... Made a Same Day Change on the outbound of a roundtrip which caused my entire ticket to be refared (technical glitch, that's not supposed to happen). Because of that, my "new" booking prompted the Mile Play bonus. I didn't look to see if I got a new 016 ticket number though, so can't tell you if that was the trigger.