is attack on titan (shingeki no kyojin) episode 58 filler?

The Owl's Titan kills off the remainder of the soldiers from Marley Public Security in front of a shocked Grisha Jaeger. As he squeezes the life out of one, he tosses his remains to the sea.

He then explains that the sea is a large body of saltwater that covers 70% of the world. After they are all dead, he leaves his Titan and climbs back on the wall where he cuts Grisha free of his bonds.

He introduces himself as Eren Kruger and explains that he possesses one of the Nine Titans. Like Grisha, he is a Subject of Ymir.