Are there other “offical” sites saying that www is deprecated?
No, because the ‘www’ prefix was never “official” in the first place. It was a de-facto convention, not an actual standard of any kind.
As that site points out, use of www makes no general sense anymore now that the web is ubiquitous. In marketing, it’s actively discouraged because it detracts from the brand name in question. The fact that it’s an internet address is obvious to anybody reading it, you don’t have to point out the fact that it’s on the World Wide Web as well.
Now, support for the www prefix is often needed to handle those users who always type it even when it’s unneeded, however having your content on both www and non-www detracts from your search engine rankings, as it’s considered to be duplicated content. The best solution is just to use the redirect method, as pointed out on that site I gave above. This lets your users see your brand identity clearly by eliminating the www even when they typed it in, and also lets search engines redirect and know not to use the www address when they find it.
