User blog comment:Omega natsu2/Chapter 368: The Third Seal, Predictions./@comment-5172158-20140119151448/@comment-7418318-20140120223259

You mean something like Ultear and Jellal suspecting that this ritual would expose a thought projection, so they temporarily switched places with Ultear using transformation magic to look like Siegrain, while Jellal let his Siegrain projection appear like Ultear?

Considering how easily fooled the council (including the chairman, who probably performed the procedure) was by "Siegrains" being accepted into the council, I could easily see why those old fools wouldn't have noticed something like that and truly believed that Jellal is now the seal, even if it was Ultear disguised as him.