Most people cant get bone dry without losing some muscle fullness. It requires water restriction for days before a competition. Some water will also be taken from their muscles.
Ya but that is not only water restriction and dryness that is also lower body fat levels. Their is always room to lose a little more fat, people think that guys like Phil and Kai are at their absolute limit, but they are not, they may have 4-5lb left of fat to lose but probably can't cause of the chemicals they are on and if they could it would be at the expense of too much fullness.
I think galeniko said it best, that absolute last layer comes from pure starvation and torture.