I’m not sure about Cashu, but a friend of mine works on the Fedimint project. Another eCash system built on top of bitcoin.

I asked him if the Mint sets the monetary policy, and he said it’s hard carded to 1:1 with sats. So no fraction reserve mint.

You can redeem your tokens, your authorization to a claim on sats, for hard sats.

Here is the docs, if you’re curious: