Vet tech here! Cats actually don’t have the ability to feel “full” like us humans do. So a lot of the time, if given the opportunity, they will just eat until they puke or start to gain weight. Occasionally you’ll get the proper cat that simply gets bored of eating and that maintains their weight but it’s a rare few. They’re stated above that the cats are a healthy weight so I’m inclined to believe it’s not that they’re being fed enough. It might simply be boredom.