In fact, that's how you delete your old tweets: rename old account to a new username, register the old username, delete the renamed account.

https://help.twitter.com/en/using-twitter/delete-tweets

See "How to delete multiple Tweets".

As bad as it sounds.

After NPR said they weren't going to post anymore because Musk decided to label them as "State Controlled Media" he made a point of saying, "OK, then we'll give your username to someone else after it expires in a month (apparently not posting for a month now expires accounts?)"

They allow it, I closed my account and days later some bot had already taken over my old username.