It applies equally well to a fiduciary coin with a promise that 1 gcoin = 1g of gold or whatever.
However, it does not necessarily apply to algorithmic stable coins (Terra) or crypto-backed overcollateralised coins (DAI). That's why I said "fiat-backed".
You don't need to see where the coins are and move to promise $1 of going for every coin.
How are you bootstrapping a network to validate private transactions without the promise of potential gains in coin value as its popularity takes off?