I'm not sure. But in the end you are laying molten plastic on top of each other. Even with a perfect flat print surface you will have slightly uneven extrusion that will be noticeable on top down lighting.
Silver cubes with direct lighting https://github.com/lord-carlos/mk3-upgrade/blob/master/asset...
Same cube with top down light: https://github.com/lord-carlos/mk3-upgrade/blob/master/asset...
What we have is Pressure Advanced. Where we stop extruding (as much) right before a corner. And we do that by doing some test prints with different values and eye balling it.
Also some firmwares like klipper have some math in it to compensate for heat expansion over time of the printers frame. Or something like that.