How is this better than a straight up escrow? You take 2x the chances of a shipping issue. Why not use an escrow to hold coins while the other party ships. Also it requires 2x the trust of the escrow here.
What? One party holds the BTC and the coin/gold and once has both releases them to buyer/seller. What is 2x risk about that?
I assume it would work like this.
Joe decides to sell Pilot (me) a .1 ounce of gold for $95.
Escrow agent (Anon) tells me to remit BTC to him. Once it's received he tells Joe to send him gold. Once that is received Anon sends Joe the BTC and Pilot (me) the gold.
That is "straight up escrow."
The risk was that the gold coin needs to be shipped twice. I am not saying this is a bad idea by any means.