The wording of Twin Universe is 'Summon an Exact Copy of the target creature.' Normally, all status effects on the creature are carried over: frozen, delay, adrenaline... This is not true with the passive skill of 'airborne'. If I web my opponent's Pegasus, and then my opponent casts Twin Universe on it, he will now have one airborne Pegasus and one on the ground. Webbing a Deja Vu before it has used its ability works the same way. I'm assuming this is a result of airborne being a passive ability.
I feel if this is intended behavior, and not a bug, it belongs on the not-a-bug list, because at the very least it is counter-intuitive to card text. It doesn't seem overpowered to me.