Yes, it is. If you choice to check it, pets and thralls will only eat the food showed when you open theyr inventory, and have prefered food.
Without that, they eat bit all, you can give fish to you thralls, or like lot, feed them honey. With diet, this change, and you have to be more carefull. Now they’re not need food to not starve anymore, it’s less tedious to do so, easier just ot feed them the good food only for fights as example.
It’s a choice, up to you, if you prefer it more real, or that they eat all.