Nothing suspicious here, the owner simply cleaned it thoroughly from dust, if it was present. Graphics cards can and actually IMO *should* always be sold clean if their owner wants to sell them easier, not only because they look better on pictures but also because the next owner won't have immediate overheating issues due to dust buildup.
On the other hand, "used" can also mean that the person used it only once or for a couple of days. It would be very hard to distinguish a card used in such way from a new one.