Most of the comments don't understand the point, and some are saying it's an April Fool's joke, but the update is obvious! - Before the update, when you clicked the "Post Video" option, a link ending with `video/1` would appear, and you could copy it, like in the image.

Now, the update simply shows the video directly instead of the link, and you can't copy the video link, but you can copy the tweet link..