The quote is talking about potentials. You are talking about what "is". Gold has a history spanning millennia. Hence your argument doesn't make sense until at least an isomorphically equal amount of time has passed during which Bitcoin could have distributed. That amount of time will be lower than for gold due to the amount of people alive now vs the amount of people alive in the past as well as developments in infrastructure (hence isomorphic).

But as is it doesn't make sense to compare the level of current decentralization of gold vs Bitcoin.