Twitter could and I hope does exactly this. Then I will charge Elon 10 BTC for the idea and send it all to Nostr devs.
Twitter would probably not do this because then it would have to support an open standard where they can’t police the content.
Oh they absolutely could. They could run their own relay and indexing service and control all content which goes in and out. It wouldn't be a vanilla experience, but it's how they would probably integrate Nostr.
But if an X user’s note ends up stored on a relay that doesn’t support delete, it’s stuck out there in the wild.
That's something they'll have to come to terms with and give users a choice to opt-in. I assume it will a check box. "Participate in Nostr: your Tweets will be sent to Nostr. Please note that doing so, your Tweets on Nostr may not be able to be deleted from all Nostr servers."
I don’t see it happening under the current regime.