Information is the company itself. In a tweet (of course), Twitter announced that "all users have the same experience on Twitter.com and can access our latest features."
When it was introduced to the world, the new (now current) look of Twitter was shown as a bold, resourceful and most updated status for the web at that time. All navigation was concentrated in the same screen by clicking the name of a user or tweet that has a media recognized by Twitter, the content is displayed in the sidebar (right).
current Twitter
How do I know that there is still a small group (almost a resistance) that used the old interface of Twitter until its last minute, my recommendation is that these people just memorize the keyboard shortcuts Twitter. So now you can use the new design of the service more easily. I dare say, more efficiently.