We are a very outdated model of human being. The last meaningful evolution of our species occurred tens of thousands of years ago when we were hunter gathers who spent a ton of calories during our daily struggle/search for food.
Your food travels through an upper and lower intestine, and finally your bowels before being expelled. The “am I hungry?” sensors are located in the early parts of that system, because again, life was a constant struggle to find enough food, so we had to ensure a constant stream of incoming nutrition.
Your lower intestine/bowel may be full, but if your stomach is empty you’re body is signally that you need to add more food to avoid breaking the chain of incoming nutrition.