Ichigo is forced to fight Zangetsu without the help of his Shikai or Bankai powers, testing his raw strength and resolve.
Like much of the original Bleach run, the story can feel "painfully slow" as it stretches out the confrontation.
“BECK [Bleach] is a breath of fresh air. The show doesn't waste any time and keeps you hooked all until the end.” Reddit · r/anime · 3 years ago
While this episode is "filler" (not based on the original manga), it is widely considered one of the better-produced non-canon segments of the series.