Why measure it that way though? Take an open chamber head. It might be .040 from the deck to head. But move .05 in, and all of a sudden it's what? When I talk about quench. I don't just mean the distance between the head and the block where the gasket sits. I'm talking the entire area between the "bottom" of the head and the deck. Not including the combustion chamber. If that makes sense, I'm probably explaining it poorly. All of that area plays a part in what we call quench.
Or think of it this way. Why do dished pistons with a quench ring exist?