Right, there's nothing special about it besides the technical limitations. But what's the alternative? With fiat you still have those technical limitations (someone could create indistinguishable counterfeit money and dump it on the market). But there's also the political risk. Someone can get power at the Fed and decide to double the money supply over night. In fact, this has happened time and time again with many fiat currencies so its not exactly an unfounded risk. That's why the precious metal standard is lower risk for arbitrary manipulation
I think there is more than technological limitations to making this happen. Not only is counterfeiting considered a major crime by the state (who has a monopoly on violence), but the amount of "money" in circulation that has a physical representation is dwarfed by "money" that does not. Even if you doubled the physical currency in circulation you'd only increase the "monetary supply" by 10% or so. Plus there are huge logistics issues with moving that much weight/volume without getting caught.
> Someone can get power at the Fed and decide to double the money supply over night.
I think that if the function of government breaks down to this extent, I will have bigger problems than currency devaluation.
The only limits on the gold supply are technological ones. If one takes an optimistic view of the future where we become a space-faring species the future supply of gold is effectively unlimited.
Edit: As much as I'm a huge crypto detractor, at least Bitcoin's supply is limited mathematically, not just circumstantially. I would argue this is a bad thing, but if you're looking for something that will hold its value due to scarcity a durable commodity we dig out of the ground seems like a bad long-term bet. What if we discover a massive gold deposit?