Here is a
LINK to a Technical Resource note from TeleWire, which is as ISO 9001 certified manufacturer of Test Leads, Wire Harness, and Cable Assembles. They also say mating Gold and Tin contacts is a no-no. A quick Google search returns that Galvanic Corrosion is not likely to occur in a PC DC power connector because it requires a liquid to act as a bridge between the Gold and Tin. The concern is
Fretting Corrosion which is caused by microscopic movement of the contacts due to thermal expansion/contraction and fan vibration, which can occur in a GPU DC power connector in a computer. I don't know how long it would take for Fretting Corrosion to become a problem in this case, but it seems to be a valid concern because over time, it causes the Gold to oxidize into a resistive film.