Part of the smoothness here is that scrolling the text is 1:1 once you get down to the sections with colored headers. It demonstrates that it's possible to make a page look fancy like that without "breaking" your intuition of what scrolling "should be."
JS animations obviously don't take the place of video/audio media that you'd play/scrub through.
JS animations obviously don't take the place of video/audio media that you'd play/scrub through.