Lol, nostr metadata leak was a criticism of NIP-04 , which has long been considered obsolete NIP-17 messages addressed this long time ago, but it was not scalable to large groups. MLS solves this problem so we finally have, scalable, private, decentralized messeging on the internet, all these specs are public, the very fact that you did not understand this, means no one will be able to make you understand with a comment.