Wouldn't you need to use that $3000 coin to pay $3000, ie use it for its face value, for this loophole to 'work'? In which case it would not be very useful...
If you use it to pay $88k then the transaction is obviously $88k although you've then paid in gold, not cash.
I feel that this is a "you can't have your cake and eat it too" situation.
Just hypothesizing, do not actually know if this is the mechanism, but it is entirely possible that by storing gold with a broker could allow them to access the value in order to make other investments. Essentially, having cash as collateral means having it in a bank and subject to these restrictions whereas gold in a 3rd party vault might not be but still give you the same access to credit.
If you use it to pay $88k then the transaction is obviously $88k although you've then paid in gold, not cash.
I feel that this is a "you can't have your cake and eat it too" situation.