Why's that? It solves the real world war origin problem. Was first mentioned in History of the Marvel Universe, so you can credit Mark Waid for it.
It is. Warbird and Threadneedle, two new characters introduced in The Marvels, were mentioned in History of the Marvel Universe. Everything else on that page of upcoming events has come to pass in the 616 universe (for example, Outlawed, Empyre, King in Black) except for the wedding of Tony Stark and Emma Frost (which makes me wonder if Hellcat was a substitution because of Marauders?).
Also, if it wasn't in continuity, why use a newbie character like Aero?