Not working, which is great. In the real world, you also can't take back what you've said.
Discussion
Yes, you can’t force delete from other people’s devices. It’s just a friendly note to save storage space and long term feed estate. There’s so much stuff on Nostr that it’s useful to drop non-important content.
The thing is once you implement in a client the option to choose delete after xyz. People will believe it's gone for real + unfortunately in many people it creates bad incentives to act like maniacs.