User blog comment:IamJakuhoRaikoben/Chapter 455: Magnolia's Defensive Battle, Review./@comment-7418318-20151005063419

I got the feeling that Zeref made this massive strike to force FT to use Fairy Heart, so he can pinpoint it's exact location.

Alternatively it could also be possible that there aren't all that many Shields present really. The three additional air-fleets and magic signatures could also be a very intricate illusion to trick FT into firing Fairy Heart. August would be a prime candidate to facilitate such a grand-scale illusion.

Though on the other hand, this could also be the perfect opportunity to bring Ivan back into the story. In the GMG he showed great skill in creating elaborate illusions, including the masking of the magic-signature of the actual fight with Laxus and while it wasn't mentioned, probably also creating fake magic-signatures for the illusionary fight.

If he got a massive boost from Zeref (something like Demonification perhaps?) or if one of the Spriggans is supplying him with power for his illusions I could see this work.