I think it's related to the fermentation going on in your stomach. I'm not sure if it's the best way to become satiated. I personally find saturated fats to be much more satiating, I can go without food for a full day without feeling hungry if I eat enough.
Fermentation happens in the gut where all the bacteria is, right? Does fullness in the gut translate to feeling full?
However, I don't think we really know where satiety comes from yet, that's why we have all of this research on the topic still. There are a few different theories, but I wouldn't call them proven.
It may not be a sensation related to some measure of the volume of matter in your gut. I think it's also related to gut microfauna such as lactobacilla, and appetite is definitely related to the brain as well through the gut, so it probably gets pretty complicated and possibly is very individualized. I'm no expert, but I do read a lot about these topics.