It's how the forum software works, different software would probably do something to pull out the necessary information to embed a tweet, this software pre-dates twitter.
All you need is the number that identifies a tweet. In the post above yours the URL is:
https://twitter.com/user/status/1557864445539323904
You just need that number, nothing else.
So it should look like this if you type it:
Or if you're using the tweet button in the editor just put in the number, nothing else.