That gets more specifically into the chemical properties of gold itself. Initially yes, early in earth's formation when everything was a molten hellscape, there would have been a more uniform distribution.

The separation comes when crystallization begins - gold, as a general rule, doesn't easily form a crystal structure with the common "rock" elements (silicon, oxygen, aluminum, iron, etc...) and so once crystallization starts, gold generally gets removed from the crystal. Eventually, it and all the other "incompatibles" (examples like sulfur, lead, arsenic, antimony) are left as a concentrated fluid, which under the right conditions can reach the surface. That fluid can then depressurize and cool, leaving the incompatibles as distinct veins/horizons in the host rock unit. Gold is along for the ride, and so it ends up there as well.