The simplest use case is to turn on the Wind Filter, which suppresses wind noise thus clearing up the audio. Mic Focus allows the microphones to follow the camera’s zoom and home in on a particular sound source.
You can also use Acoustic Focus if you want to control the directionality of the microphones separately from the zoom (this is available in Pro video mode).
By the way, the Asus ROG Phone 3 also uses Nokia OZO technology for its camera. While the OZO VR department shut down, the OZO Audio team has been going strong – besides Asus, Oppo and OnePlus use Nokia’s tech.