To create the time dilation effects seen in the movie, the black hole would have to spin very fast and drag light to one side, making the central disc seems squashed. Nolan thought this asymmetry would confuse the audience and slowed it down.
The result looked good, but the central black hole seemed to be squashed up against one side. That’s because the movie’s time dilation effects meant the black hole had to spin very fast, causing it to drag the light to one side. Nolan didn’t like this asymmetry and thought moviegoers wouldn’t understand why, so the team slowed it down, says James.