is attack on titan (shingeki no kyojin) episode 43 filler?

In the Underground Chapel, Eren Jaeger struggles to free himself as Historia Reiss approaches. She tries to reassure Eren and says that her father is an ally to humanity, and that they were wrong about him.

Historia says that her father had no choice when it came to the orders he gave regarding the Scouts and the killing of Pastor Nick. Rod Reiss arrives and says that he will explain the rest, causing Eren to remember his kidnapping and wonder how much time has passed.

He notices the unusual glowing crystals that form the walls of the cavern and realizes that this place seems familiar to him.