Well, OK, so when should I expect that I can build a brochure site for a hotel that uses HTML5 videos and have one video format and one set of custom controls to work with? Because the world has moved on and Flash is no longer a viable option for this kind of work despite offering those advantages for many years, thanks to much the same browser developers who can't get their act together and actually provide a better replacement. They can't even manage to make the default "this is a video" overlay look the same, or even put it in roughly the same place so you can design placeholder graphics accordingly.
Please explain what this has to do with validation, which I thought was the topic under discussion?
But this brings us back to the original question from my first post in this thread: why? What objective advantage do you or your employer/client gain by insisting on such compliance?
Exactly what it is supposed to do: assurance that it will work as built across all major browsers.
Believe it or not, a majority of big-name sites are still using Flash, along with open-source JS players.
It seems to me you're complaining that using new features that aren't yet standardized, aren't yet standardized. I can sympathize with your frustration, but then if you don't like it, don't use them.
Browsers will never be "standardized" on the very latest features. That's not how it works. So if you don't want to get stuck, don't use the latest features. What else do you expect me to say?