That depends on what do you mean by hard money. A capped supply?
Bitcoin is the only commodity on the planet who's supply is completely unaffected by demand.
An emission like 1 per second forever is much more immutable due to guaranteed miner incentives and lack of arbitrariness. And thus a better basis for hard money [2].
[1] https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2022...
[2] https://john-tromp.medium.com/a-case-for-using-soft-total-su...