Pay particular attention to the part that says:
The archaeologists also found a gold relief showing the four sons of the Egyptian god Horus, other plaster masks of women's faces, several glass and clay utensils and some metal coins.
The metal coins are being checked to see whether they can date the era of the tomb more precisely.
Those coins, found in context, are being used to help date a unique site. What knowledge would have been lost if someone with a metal detector had gotten there first and yanked those coins out of the ground? What other damage would have been done to the site in the process?
How can anyone read that article and not agree that coins are indeed archaeological artifacts, deserving of the same protection and subject to the same restrictions?