Height isn't everything, the shape of the track, wheel compounds of the trains etc make a lot of difference. Big One has a slow, medium and fast train so it can operate in windy conditions, and the medium train on a non windy day is the fastest it can reach (I believe that the fast train runs too fast on a day with no wind at all).The fact remains, that Air was not the first flying coaster.
I'm not defending either claim, neither are acceptable but there's not much that can be done about it.