I remember reading somewhere that the signal from the stomach to the brain telling you are full takes 20 minutes so if you eat slower you eat less food in that period when you are full but don't know it yet
Both systems make sense, since you can hydrate in ~60 seconds but might need to stay hungry for ~10 minutes after you start eating. But they can both cause problems: hunger by prompting fast eaters to overeat, and thirst by letting dehydrating things like liquor satiate you.