This is simply a case of an out-of-date reference blog post (that 2010 #newtwitter article). Quick observation of Twitter.com today will reveal that it's no longer using the public API (at least from the client). It's fetching the Tweets from the server pre-rendered (via http://twitter.com/i/timeline). So nothing to see there. Maybe taking a closer look at Twitter for iOS, which does receive promoted Tweets, would provide more information.