PC World, for example, writes:
Internet Explorer 9 has topped all other browsers in conforming with the HTML5 specification, including Google Chrome and Firefox, according to tests carried out by the World Wide Web Consortium.
This would be quite amazing if it was true. But it isn't. You can't draw such conclusions based on those tests. …
Webmonkey gets it right:
The reason IE9 tops the W3C’s list is that the test looks at only a fraction of the HTML5 spec. In other words, the test is very limited. Even better, it’s limited to things IE9 is good at.
The article is a recommended read for anyone who wants to understand what's actually going on here. Unfortunately, they are referring to the flawed html5test.com site (which doesn't test just HTML5, and which uses a strange way to assign scores), but that's a different story… Do read the article if you want to learn more about the test that is claimed to declare IE9 as the HTML5 leader.
There are also some comments from various browser vendors on the HTML test suite mailing list on the subject. For example, there seem to be bugs that affect the pass percentages, and the results for Opera are reportedly "partly bogus".
Needless to say, "IE9 wins at HTML5" is now all over the web. Unfortunately, I doubt that most of the articles that declare IE9 the "winner" are going to be updated to reflect the reality of the situation.
Yet another major PR win for Microsoft, then.