The mod description is incorrect due to a change on how vanilla minecraft works.
At starting with snapshot 21w37a chunk render in a cylinder shape.
https://minecraft.fandom.com/wiki/Java_Edition_21w37a

Render distance now causes chunks to load in a cylinder shape around the player instead of a square.

The mod still renders chunks in a circle, but the fog is rendered in a cyllinder.

ye I know, just didnt want an explanation for each minecraft version on the page. Added a small note