is attack on titan (shingeki no kyojin) episode 51 filler?

The Beast Titan and its companion Titans stand outside Shiganshina District as the Scout Regiment awaits them on top of the Wall. Behind the Scouts, Reiner Braun hardens the fingers and toes of his Armored Titan to begin climbing the Wall.

Erwin orders the Scouts to avoid fighting the Armored Titan and to stay away from it. A little further down the Wall, Eren Jaeger asks why Erwin does not give the order to attack.

Hange Zoë replies that he is watching the enemy's movements, because Reiner and the others clearly have something prepared for them.