What makes you think it's WebGL? It looks like an mp4 to me, at least I was able to download the mp4. It's sharp because it's high resolution.
But maybe they're serving different content depending on the client.
But maybe they're serving different content depending on the client.
I had no idea videos on mobile sites could look that sharp and well integrated… I guess I’m used to seeing them done so badly this one stuck out, so I thought it had to be WebGL