What evidence is there that anything Chrome specific was used? Safari’s WebGL support has come later than others, and there are reports of WebGL being slower on Safari than Chrome, for example https://developer.apple.com/forums/thread/696821 It’s possible your incredulity maybe should be directed towards Safari and not someone trying to do their best?

Despite using firefox and wantind cross browser projects I think the learning involved in browser compatibility is a LOT less interesting then about the math behind animation.