is bleach: thousand-year blood war (bleach: sennen kessen-hen) episode 21 filler?

In the distant past, an infant Yhwach matures into a young man after absorbing the power of thousands of people who have linked their Souls to his. In the present, Yhwach awakes on his throne and thanks the Souls of the dead for letting him wake to see another day before telling Uryū Ishida to bid farewell to this abominable world because there is no turning back.

Meanwhile, the stone fort created by Gremmy Thoumeaux crumbles in the wake of his death.