If I'm understanding this correctly, the Lightning node used by the Cashu gateway is not the same Lightning node that's used by the Cashu mint.
That's quite the privacy improvement!
Discussion
It gets better: the Lightning node used by the Cashu gateway could be your nostr-native mobile Lightning wallet, accepting payment gateway requests from other users over nostr.
No IPs. No direct connections. Nobody to stop them. Just two people doing their thing over a network that helps them find each other and organize.