Gold is classified as a commodity. The Commodity Futures Trading Commission (CFTC) is the federal government agency that regulates the commodity futures and other commodity derivatives, not the SEC.
It almost seems like there is no regulation nor clear guidance and even different arms of the government can't decide which it is.
https://fortune.com/crypto/2023/03/08/stablecoins-ether-comm...
Each agency is going to make a good-faith judgement as to whether they have jurisdiction, and if that means 2 or more agencies start telling you what you have to do...well, maybe you shouldn't have leaped with both feet into a brand-new area where the regulations were unclear just because you thought you could make a quick buck, hmm?