is bleach: thousand-year blood war (bleach: sennen kessen-hen) episode 12 filler?

Twenty years ago, in the meeting hall of the First Division barracks, 10th Division Captain Isshin Shiba concludes his report to the other captains and Captain-Commander Genryūsai Shigekuni Yamamoto, who affirms his understanding of the situation and notes that while an unauthorized excursion is a violation of their laws, Isshin's quick and decisive action helped minimize Shinigami casualties and prevented excessive damage to the Human World, which is why Yamamoto will overlook this violation.