It’s not that complex, but it’s deeply un-intuitive from a game perspective. Most people play games, and they eat food when the game says they’re hungry, hunger goes away, comes back later. Simple.
In this case you have two different concepts that mean two completely different things, and frankly, it ISN’T the case that people are particularly good at understanding the difference between fullness and starvation even in real life. If they were, obesity would be far easier to avoid. Your body frankly doesn’t care much - for the most part, if your stomach is empty you’re hungry, if it’s full you aren’t. As long as you aren’t in the habit of eating grass and rocks, this will get you through the day most of the time.
Humans have the opposite problem in modern times, we eat food that is very high in calories, and very quick to digest, which makes us hungry much more often than we should be, leading to easy obesity.
So no, it isn’t a system people intuitively understand, in games OR in real life.