is attack on titan (shingeki no kyojin) episode 27 filler?

In Trost District, a soldier of the Garrison arrives to warn Commander Dot Pyxis and Captain Hannes of Wall Rose's breach. That night in Stohess District, the Scout Regiment prepares to venture southwestward to assist in dealing with the Titan invasion.

Armin joins Eren and Mikasa at their carriage, wondering if Titans would be able to breach the Walls with Titans within them. Eren reminds Armin of the fall of Shiganshina, but Armin points out that a gate and not the Wall itself was breached.