Wut? It's precisely the opposite. Natural patterns have infinite complexity as you zoom in, and human-made patterns (most often) not.
"Visual complexity" is just wrong: simple black / hot pink stripes are visually exhausting upon immediate perception, whereas the monochromatically brown detail of a tree trunk is only visually exhausting on close inspection.
God, what a useless website. I hate LLMs. The actual paper is here: https://www.mdpi.com/2411-5150/10/2/34
That's precisely what they're wrong about.
Take a look at tree branches. A field of grass. A stone cliff.
Now take a look at human-made decor: drywall, plastic, laminated boards.
Which one has more visual detail?
I dunno if I agree with their arguments in the paper (there seem to be some pretty big questions unanswered yet, which the authors acknowledge), but there's definitely something to the idea that natural environments aren't as stressful for us, even if they're objectively "busier".
The default visual circuits in our brains may have evolved to optimally handle fractal patterns and textures. Straight lines, geometrical figures and featureless surfaces may require activation of less optimal circuits. Anecdotally, I find being in environments made of featureless geometrical figures uncomfortable to be in.