User blog comment:Omega natsu2/Episode 185: Erza vs. Kagura, Review./@comment-5303512-20140610014116/@comment-7418318-20140610090446

Since he also knew that Lucy was the one who closed the Gate, my best guess would be that the information about the almost invaison and Lucy preventing it somehow leaked past Doranbolt's measures.

Alternatively, maybe with no F-Rogue being in that timeline, the Royals managed to capture the F-Lucy of that timeline and learned about the invasion from her. That would enable the King to make a speech similar to what he did in the chapter "Union".

But you're right, that's another point to add to my previous list.