I believe similar results are acheived with NIP59 and NIP101:
https://github.com/nostr-protocol/nips/blob/fd914c600fd590e6188534cd7555116da7855503/59.md
https://github.com/water783/nips/blob/nip101/101.md
This chat app that is in beta uses them. No metadata leak about who is speaking with who:
It's just a matter of client adoption I think.