They don't... To the best of my knowledge.
Doesn't nostr:nprofile1qqs9ajjs5p904ml92evlkayppdpx2n3zdrq6ejnw2wqphxrzmd62swspzemhxue69uhhyetvv9ujuvrcvd5xzapwvdhk6qgdwaehxw309aukzcn49ekk2qghwaehxw309aex2mrp0yh8x6tpd4ehgu3wvdhk6ynf30t use this? How do they get past these problems
Discussion
They do use this https://github.com/water783/nips/blob/nip101/101.md
Yep, but secret chats run into the same issue that you have to trust your peer and their relays to not identify you.
nostr:npub1tm99pgz2lth724jeld6gzz6zv48zy6xp4n9xu5uqrwvx9km54qaqkkxn72 implements NIP-17 (gif-wrapped messages)