That's not backing.

When FRNs were backed by gold you could take them to the Federal Reserve (or the US Treasury) and demand gold.

The issuer who created the notes "backed" them by pledging a real asset - the notes were merely a stand-in for that real asset.

I don't have a particular right to go to the miner & demand any particular amount of energy for my Bitcoin.

Similarly, gold takes energy to find, recover & refine, but it is not backed by that energy. If you think it is, then we could ask what backs the energy. Hopefully you see why this leads quickly to absurdity.