Got it

So the mint can technically mint and burn at will, it’s just that the Cashu implementation does this with LN sends and receives

I’m assuming it’s similar with fedimint but also including on-chain?

So from a very literal standpoint the ecash is an IOU from the mint, and while in practice this redemption is meant to be automatic and programmable, this functionality can be broken (by for example a bad actor or just code bugs, etc)

I say this to distinguish it from LN which has a redeem-ability that generally speaking can’t really be broken (it’s MUCH more trust-minimized)