Suffice it to say that just examining the chart for the 90s shows no clear relation between the real rate and the price of gold. If a regression analysis were done R squared would not be impressive.
As to his puzzle about money growth and inflation rates even ancient monetary theory tells one that the velocity of circulation of money, V, is a principal component of prices. V has dropped rapidly since 9/11 because of uncertainty and people and business cutting back on spending, investing. While "fiat money" is a common term it is not an accurate or especially meaningful one. When people have decided that money is of no value no "fiat" will make it so. The value had gone from the Continental currency by 1785, the Condederate by 1864 and the German by 1922. Fiat or no fiat.
But I wouldn't expect fans of the purdy metal to get into all that complexity or give up a term supporting their ideology.