I've been told this at least three times now on HN over the years (pretty soon I'm going to start keeping a list of URLs so people know I'm not exaggerating.) Every single time it turns out that it isn't actually true.
It was added to desktop Safari. iOS Safari supports VP9 only in WebRTC. It may have changed, but I can't find any evidence that it has.
If you see it working somewhere, it is almost definitely using the polyfill[1].
