Looks like that's not correct. If you open your browser console with the React developer tools extension installed, you can see that not only is the canvas built with the DOM, but it's rendered with React, too.
That’s right, it’s React all the way down. It could render using anything, really; the React rendering part is quite loosely coupled from the main “what needs to be rendered” application layer.
That's actually super interesting. I would love to read a deeper dive on how you keep it so smooth, if that's something you'd be willing to share.