http://www.pcgamer.com/evga-announces-trio-of-z370-motherboards-with-cable-cutouts/

EVGA is adding to the growing pile of Z370-chipset motherboards designed for Intel's 8th generation Core processors (Coffee Lake). The company announced three new models, each of which contain power connector cutouts to make it easier to route cables.

These little sections of sliced PCB can be helpful in maintaining a clean layout, though that's partially dependent on your case—ideally there would be a cable cutout nearby to tuck the power cable neatly out of sight.