Afaik no developed-country government “backs” gold in any meaningful way. There are some reserves here and there, some historical, but they are not directly linked to liquidity. It’s just a market for a commodity that happens to be fairly practical to store value in. Whether governments will start using digital commodities in the same way, is really a political question. I agree that it might be a cornered market, but the fact that forks do seem to happen might well turn out to be the way out of that problem.
That’s not “backing”: nobody buys specifically to keep gold prices up or to legitimise the trade, they just use it as a commodity to make their creditworthiness believable and storing their value in a practical way. They are leveraging a pre-existing market, not backing it.
(As a side note, this role for gold is clearly legacy: look at how little gold China stores, compared to their overall reserves.)
