I don't have a problem with that. It's redeemable for bitcoin and represents bitcoin since those sats are from a Lightning node and those sats are locked in a smart contract on the time chain.
Cashu isn’t locked anywhere. The mint just “tells” you they have them. Unless this is a different type of implementation. The mint can empty out the sats and just say they left them there.
Good ole Cashu. A way to get rugged privately. I'm not a Cashu bear, but I'm not a bull either. I think it's a very cool technology and it has use cases, but if you're using it, it needs to be for temporary storage of your funds. You should migrate them to a wallet that you own ASAP. i.e. Peg-in and peg-out immediately for privacy reasons.