It's funny he answered the question the exact same way Jeff Bezos did.
It's good to see journalists asking these questions now.
The answer he gave is obvious nonsense though. Technically if that was their goal they could still use an industry standard format and then convert it to a proprietary format to make the screen rendering faster. The end user wouldn't need to know that the proprietary format was used. It's one of those answered designed to sound plausible but isn't.
Of course if he answered, "we do it to make it difficult for our customers to get content from other sources", then he probably wouldn't have a job very long.