Spot is an over-the-counter consensus, not an exchange ticker
Unlike a share, gold has no single listing venue whose last trade defines the price. The overwhelming majority of physical gold changes hands over the counter between banks, refiners and brokers, settled through London vaults. The spot price is therefore a consensus of what those participants are quoting at a given instant, aggregated from the most liquid venues. Two data providers can legitimately differ by a few cents at the same timestamp for this reason — neither is wrong.