There is no downside for the FFL to sell the gun to you after 3 days. They get their money, if it eventually comes back denied the scumbag goes to jail and in some cases the guns have been given back to the FFL to sell again.
Well in this case the dealer who is doing the transfer is not the one who he bought it from so it isn't like he can do a credit card chargeback (worst case scenario) if they don't want to give him the gun.
If I had AR10 money tied up in a purchase and the dealer told me he may never release it I would not be too thrilled with him.