The W3C document may be relevant to some small minority but the majority of people developing using HTML5 are targeting a set of clients that mostly or entirely

The W3C document may be relevant to some small minority but the majority of people developing using HTML5 are targeting a set of clients that mostly or entirely follow the WHATWG's version in their actual implementations, and this is what defines relevance. The creation of the WHATWG was obviously a bad day for web standards, but at this point one has to be pragmatic. The existence of the W3C spec only adds confusion, and little to no value.