Why is it that Distant Horizons renders like this?

I'm running Distant Horizons from the Iris installation 1.20.4, not sure which Distant Horizons version I just see 0.15.7. When I click 128 chunks on a singleplayer world, it only renders seemingly 64 chunks but not the full amount. (maybe it is 128 and it isn't as impressive since the wider the area the more chunks required to double the length) It only increases to the desired chunk generation when I go there with my player and manually load in the chunks. Is there an option in Distant Horizons I can enable to get the full desired chunk generation? Does this require an external mod that preloads more chunks? If you'll notice in the third picture it is obvious which chunks were loaded by default and which ones I loaded manually. Could this be a ram bottle necking issue because I see stray chunks very far out which could be the size it was supposed to render at. There is one near the top middle, in the image taken from the tallest height. (I can't say figure one because I can't label images, please implement that feature)