This is sort of like a dictionary writer giving up on trying to "standardize" English and just documenting common use. It's descriptive, not prescriptive. The web changes and they just try to keep up.
What it also says is that a browser is never done, and if you don't have a dedicated team creating new versions, you're not going to keep up. The idea that you can specify software, build it, and then use it without changing it is nonviable when it comes to HTML in the wild.
That fits the web as it exists today, but I wonder whether it will slow down in a few years, when devices aren't changing much and browser vendors want to redeploy their browser teams to the new shiny.